\input texinfo
@setfilename kpathsea.info
@settitle Kpathsea: A library for path searching

@set version 6.4.2/dev
@set month-year January 2026

@copying
This file documents the Kpathsea library for path searching.

Copyright @copyright{} 1996--2026 Karl Berry & Olaf Weber.

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries a copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).
@end ignore

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation
approved by the @TeX{} Users Group.
@end copying

@c Define new indices for commands, filenames, and options.
@defcodeindex cm
@defcodeindex fl
@defcodeindex op

@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex cm cp
@syncodeindex fl cp
@syncodeindex fn cp
@syncodeindex ky cp
@syncodeindex op cp
@syncodeindex pg cp
@syncodeindex tp cp
@syncodeindex vr cp

@dircategory TeX
@direntry
* Kpathsea: (kpathsea).                       File lookup along search paths.
* kpsewhich: (kpathsea)Invoking kpsewhich.    TeX file searching.
* mktexfmt: (kpathsea)mktex scripts.          Format (fmt/base/mem) generation.
* mktexlsr: (kpathsea)Filename database.      Update ls-R.
* mktexmf: (kpathsea)mktex scripts.           MF source generation.
* mktexpk: (kpathsea)mktex scripts.           PK bitmap generation.
* mktextex: (kpathsea)mktex scripts.          TeX source generation.
* mktextfm: (kpathsea)mktex scripts.          TeX font metric generation.
@end direntry


@titlepage
@title Kpathsea library
@subtitle for version @value{version}
@subtitle @value{month-year}
@author Karl Berry
@author Olaf Weber
@author Taco Hoekwater
@author @url{https://tug.org/kpathsea}

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage


@contents


@ifnottex
@node Top
@top Kpathsea library

This manual documents the Kpathsea library for path searching.  It
corresponds to version @value{version}, released in
@value{month-year}.

@menu
* Introduction::             Overview and history.

* unixtex.ftp::              Obtaining @TeX{} software.
* Security::                 Who can write what files, etc.
* TeX directory structure::  Managing the horde of @TeX{} input files.

* Path searching::           How filename lookups work.
* TeX support::              Special support for TeX-related file lookups.

* Programming::              How to use Kpathsea features in your program.

* Reporting bugs::           Where and how to report bugs.
* Index::                    General index.
@end menu
@end ifnottex


@node Introduction
@chapter Introduction

@cindex introduction
@cindex fundamental purpose of Kpathsea

This manual corresponds to version @value{version} of the Kpathsea
library, released in @value{month-year}.

The library's fundamental purpose is to return a filename from a list of
directories specified by the user, similar to what shells do when
looking up program names to execute.

@cindex programs using the library
The following software, all of which is maintained in parallel, uses
this library:

@itemize @bullet
@item Dviljk (see the @samp{dvilj} man page)
@item Dvipsk (@pxref{,,,dvips, Dvips: A DVI driver})
@item GNU font utilities (@pxref{,,,fontu, GNU font utilities})
@item Web2c (@pxref{,,,web2c, Web2c: A @TeX{} implementation})
@item Xdvik (see the @samp{xdvi} man page)
@end itemize

@noindent Other software that we do not maintain also uses it.

Kpathsea is now maintained as part of the @TeX{} Live distribution
(@url{https://tug.org/texlive}), which includes several more
Kpathsea-using programs.  For information on configuration, building,
installing, and more, @pxref{,,,tlbuild, Building @TeX{} Live}.

@cindex interface, not frozen
@cindex comments, making
@cindex suggestions, making
The library is still actively maintained.  If you have comments or
suggestions, please send along (@pxref{Reporting bugs}).

@cindex conditions for use
@cindex license for using the library
@cindex GNU General Public License
The Kpathsea library is distributed under the GNU Library General
Public License (LGPL), version@tie{}2.1 or (at your option) any later
version.  In short, this means if you write a program using the
library, you must (offer to) distribute the source to the library,
along with any changes you have made, and allow anyone to modify the
library source and distribute their modifications.  It does not mean
you have to distribute the source to your program using the library,
although we hope you will.  See accompanying files for the text of the
GNU licenses, or @url{https://gnu.org/licenses}.

@cindex @TeX{} Users Group
If you know enough about @TeX{} to be reading this manual, then you (or
your institution) should consider joining the @TeX{} Users Group (if
you're already a member, thanks!).  TUG produces the periodical
@cite{TUGboat}, sponsors an annual meeting and publishes the
proceedings, and arranges courses on @TeX{} for all levels of users
throughout the world.  See @url{https://tug.org} for information.

@menu
* History::
@end menu


@node History
@section History

@cindex history of Kpathsea

@cindex Knuth, Donald E.
This section is for those people who are curious about how the library
came about.  If you like to read historical accounts of software, we
urge you to seek out the GNU Autoconf manual and the ``Errors of
@TeX{}'' paper by Don Knuth, published in his book @cite{Digital
Typography}, among other places.

@cindex Morgan, Tim
@cindex Rokicki, Tom
@cindex Berry, Karl
@cindex VAX 11/750
@cindex Sun 2
@pindex pxp @r{Pascal preprocessor}
@pindex pc @r{Pascal compiler}
[Karl writes.]  My first ChangeLog entry for Web2c seems to be
February 1990, but I may have done some work before then.  In any
case, Tim Morgan and I were jointly maintaining it for a time.  (I
should mention here that Tim had made Web2c into a real distribution
long before I had ever used it or even heard of it, and Tom Rokicki
did the original implementation.  When I started, I was using
@code{pxp} and @code{pc} on VAX 11/750's and the hot new Sun 2
machines.)

It must have been later in 1990 and 1991 that I started working on
@cite{@TeX{} for the Impatient}. Dvips, Xdvi, Web2c, and the GNU
fontutils (which I was also writing at the time) all used different
environment variables, and, more importantly, had different bugs in
their path searching. This became extremely painful, as I was stressing
everything to the limit working on the book.  I also desperately wanted
to implement subdirectory searching, since I couldn't stand putting
everything in one big directory, and also couldn't stand having to
explicitly specify @file{cm}, @file{pandora}, @dots{} in a path.

@cindex Vojta, Paul
In the first incarnation, I just hacked separately on each
program---that was the original subdirectory searching code in both
Xdvi and Dvips.  That is, I tried to go with the flow in each program,
rather than changing the program's calling sequences to conform to new
routines.

Then, as bugs inevitably appeared, I found I was fixing the same thing
three times (Web2c and fontutils were already sharing code, since I
maintained both of those---there was no Dvipsk or Xdvik or Dviljk at
this point).  After a while, I finally started sharing source files.
They weren't yet a library, though.  I just kept things up to date
with shell scripts.  (I was developing on a 386 running ISC 2.2 at the
time, and so didn't have symbolic links.  An awful experience.)

@cindex MacKenzie, David
The ChangeLogs for Xdvik and Dvipsk record initial releases of those
distributions in May and June 1992.  I think it was because I was tired
of the different configuration strategies of each program, not so much
because of the path searching.  Autoconf was being developed by David
MacKenzie and others, and I was adapting it to @TeX{} and friends.

@cindex zuhn, david
I started to make a separate library that other programs could link with
on my birthday in April 1993, according to the ChangeLog.  I don't
remember exactly why I finally took the time to make it a separate
library; a conversation with david zuhn initiated it.  Just seemed
like it was time.

@cindex Walsh, Norman
@cindex Neumann, Gustaf
Dviljk got started in March 1994 after I bought a Laserjet 4.  (Kpathsea
work got suspended while Norm Walsh and I, with Gustaf Neumann's help,
implemented a way for @TeX{} to get at all those neat builtin LJ4 fonts
@dots{} such a treat to have something to typeset in besides Palatino!)

By spring of 1995, I had implemented just about all the path-searching
features in Kpathsea that I plan to, driven beyond my initial goals by
Thomas Esser and others.  I then started to integrate Web2c with
Kpathsea. After the release of a stable Web2c, I hope to be able to stop
development, and turn most of my attention back to making fonts for GNU.
(Always assuming Micros**t hasn't completely obliterated Unix by then,
or that software patents haven't stopped software development by anybody
smaller than a company with a million-dollar-a-year legal budget.  Which
is actually what I think is likely to happen, but that's another
story@dots{})

@cindex Weber, Olaf
[Olaf writes.]  At the end of 1997, Unix is still alive and kicking,
individuals still develop software, and Web2c development still
continues.  Karl had been looking for some time for someone to take up
part of the burden, and I volunteered.

@cindex Hoekwater, Taco
@cindex Breitenlohner, Peter
[Karl writes again.]  Indeed, time goes on.  As of 2006 or so, Olaf's
available time for Kpathsea was reduced, and I started taking overall
care of it again, although I did not do any significant new
development.  In 2009, Taco Hoekwater implemented a major
rearrangement to make the library suitable for use within the MetaPost
library (@pxref{Programming overview}).  Also, for some years now,
Peter Breitenlohner has made many improvements to the infrastructure
and kept it up-to-date with respect to the overall @TeX{} Live build,
where Kpathsea is now maintained.


@c emacs-page  separate file so we can easily generate unixtex.ftp.
@include unixtex.texi


@node Security
@chapter Security

@cindex security considerations

None of the programs in the @TeX{} system require any special system
privileges, so there's no first-level security concern of people gaining
illegitimate root access.

Thus, the general goal of our security measures is to make an
untrusted @TeX{} document safe to execute, in the sense of no document
being able to change the system or user configuration, or transmit
information to an attacker.  Here are some of the steps that have been
taken to make the @TeX{} system safe in this regard:

@itemize
@item
@cindex trojan horse attack
@flindex .profile@r{, (un)writable by @TeX{}}
@findex \openout
A @TeX{} document can write to arbitrary files via @code{\openout},
e.g., @file{~/.profile}, and thus an unwitting user who runs @TeX{} on
an untrusted document is vulnerable to a trojan horse attack.  This
loophole is closed by default, but you can be permissive if you so
desire in @file{texmf.cnf}; see the variable @code{openout_any}.
@xref{tex invocation,,, web2c, Web2c}.  MetaPost has the same issue
(Metafont cannot write arbitrary files).

@item
@cindex shell commands, security
Dvips, Xdvi, @TeX{}, and others can execute shell commands.  By
default, only a handful of commands that are believed to be safe, to
the best of our ability to check, are allowed.  For the list, see the
@code{shell_escape_commands} variable in @file{texmf.cnf}
(@pxref{Shell escapes,,, web2c, Web2c}).  For more information, e.g.,
to disable this completely, see the @samp{-R} option in @ref{Option
details,,, dvips, Dvips}, the xdvi man page, and @ref{tex
invocation,,, web2c, Web2c}, respectively.

@item
@cindex Lua@TeX{} and security
@cindex kpse mode of Lua@TeX{}
@cindex Con@TeX{}t and (no) security
Lua@TeX{} is a special case.  Since Lua is a general-purpose
programming language, it has all the usual functionality for writing
files, executing shell commands, opening network connections, and
plenty more.  When Lua@TeX{} is used in its so-called ``kpse'' mode,
as with Lua@LaTeX{}, we have nevertheless done our best to also make
it safe to execute by default, by disabling or restricting the various
problematic Lua features.  @xref{Safe filenames}, for a bit more about
this.  (When Lua@TeX{} is run in non-kpse mode, as with Con@TeX{}t
MkIV, everything is allowed; thus, untrusted documents should not be
processed.)

@item
@cindex crashes of @TeX{} and security
There are some well-known ways to crash @TeX{}, using arithmetic
overflow, which Knuth deliberately left unchecked, and other nefarious
constructs; some are listed at
@url{https://tug.org/texmfbug/nobug.html}.  While disturbing, @TeX{}
has no special system access and so these crashes don't present a
security risk.

@item
One more issue is the desire for a globally writable font cache
directory; see the section below for this (@ref{Global font cache and
security}).

@end itemize

@menu
* Global font cache and security::
@end menu

@node Global font cache and security
@section Global font cache and security

@cindex local cache of fonts
@cindex cache of fonts, local
It's useful to make arbitrary fonts on user demand with @code{mktexpk}
and friends.  Where do these files get installed?  By default, the
@code{mktexpk} distributed with Kpathsea assumes a world-writable
@file{/var/tmp} directory; this is a simple and convenient approach,
but it does not suit all situations, because it means that a local
cache of fonts is created on every user's system.

@cindex globally writable directories
To avoid this duplication, many people consider a shared, globally
writable font tree desirable, in spite of the potential security
problems.  To do this you should change the value of @code{VARTEXFONTS}
in @file{texmf.cnf} to refer to some globally known directory.
@xref{mktex configuration}.

@cindex append-only directories and @code{mktexpk}
The first restriction you can apply is to make newly-created directories
under @file{texmf} be append-only with an option in @file{mktex.cnf}.
@xref{mktex configuration}.

@cindex group-writable directories
@cindex setgid scripts
Another approach is to establish a group (or user) for @TeX{} files,
make the @file{texmf} tree writable only to that group (or user), and
make @code{mktexpk} et al.@: setgid to that group (or setuid to that
user).  Then users must invoke the scripts to install things.  (If
you're worried about the likelihood of security holes in scripts, you
could write a C wrapper to exec the script.)

@cindex file permissions
@cindex permissions, file
The @file{mktex@dots{}} scripts install files with the same read and
write permissions as the directory they are installed in.  The
executable, sgid, suid, and sticky bits are always cleared.

@cindex directory permissions
@cindex permissions, directory
Any directories created by the @file{mktex@dots{}} scripts have the
same permissions as their parent directory, unless the
@code{appendonlydir} feature is used, in which case the sticky bit is
always set.

Nowadays, with bitmap files rarely used, and with individual systems
being so much more powerful, this is less of an issue than in the
past. But the question still comes up occasionally.


@node TeX directory structure
@chapter @TeX{} directory structure

@vindex TEXMF
@cindex @TeX{} directory structure
@cindex directory structure, for @TeX{} files
@cindex skeleton @TeX{} directory
@cindex TDS

This section describes the default installation hierarchy of the
distribution.  It conforms to both the GNU coding standards and the
@TeX{} directory structure (TDS) standard.  For rationale and further
explanation, please see those documents.  The GNU document is
available from @url{https://gnu.org/prep/standards}.  The TDS
document is available from @url{https://ctan.org/pkg/tds}
(@pxref{unixtex.ftp}).

In short, here is a skeleton of the default directory structure,
extracted from the TDS document:

@example
@var{prefix}/      @r{installation root (@file{/usr/local} by default)}
 bin/         @r{executables}
 man/         @r{man pages}
 include/     @r{C header files}
 info/        @r{GNU info files}
 lib/         @r{libraries (@file{libkpathsea.*})}
 share/       @r{architecture-independent files}
  texmf/      @r{TDS root}
   bibtex/     @r{Bib@TeX{} input files}
    bib/        @r{Bib@TeX{} databases}
     base/       @r{base distribution (e.g., @samp{xampl.bib})}
     misc/       @r{single-file databases}
     @var{pkg}/       @r{name of a package}
    bst/        @r{Bib@TeX{} style files}
     base/       @r{base distribution (e.g., @samp{plain.bst}, @samp{acm.bst})}
     misc/       @r{single-file styles}
     @var{pkg}/       @r{name of a package}
   doc/         @r{additional documentation}
   dvips/       @r{@samp{.pro}, @samp{.ps}, @samp{psfonts.map}}
   fonts/       @r{font-related files}
    @var{type}/         @r{file type (e.g., @samp{tfm}, @samp{pk})}
     @var{mode}/          @r{type of output device (types @samp{pk} and @samp{gf} only)}
      @var{supplier}/       @r{name of a font supplier (e.g., @samp{public})}
       @var{typeface}/        @r{name of a typeface (e.g., @samp{cm})}
        dpi@var{nnn}/           @r{font resolution (types @samp{pk} and @samp{gf} only)}
   metafont/    @r{Metafont (non-font) input files}
    base/        @r{base distribution (e.g., @samp{plain.mf})}
    misc/        @r{single-file packages (e.g., @samp{modes.mf})}
    @var{pkg}/           @r{name of a package (e.g., @samp{mfpic})}
   metapost/    @r{MetaPost input files}
    base/        @r{base distribution (e.g., @samp{plain.mp})}
    misc/        @r{single-file packages}
    @var{pkg}/           @r{name of a package}
    support/     @r{support files for MetaPost-related utilities (e.g., @samp{trfonts.map})}
   mft/         @r{@samp{MFT} inputs (e.g., @samp{plain.mft})}
   tex/         @r{@TeX{} input files}
    @var{format}/         @r{name of a format (e.g., @samp{plain})}
     base/        @r{base distribution for @var{format} (e.g., @samp{plain.tex})}
     misc/        @r{single-file packages (e.g., @samp{webmac.tex})}
     local/       @r{local additions to or local configuration files for @var{format}}
     @var{pkg}/           @r{name of a package (e.g., @samp{graphics}, @samp{mfnfss})}
    generic/     @r{format-independent packages}
     hyphen/      @r{hyphenation patterns (e.g., @samp{hyphen.tex})}
     images/      @r{image input files (e.g., Encapsulated PostScript)}
     misc/        @r{single-file format-independent packages (e.g., @samp{null.tex}).}
     @var{pkg}/           @r{name of a package (e.g., @samp{babel})}
   web2c/        @r{implementation-dependent files (@file{.pool}, @file{.fmt}, @file{texmf.cnf}, etc.)}
@end example

Some concrete examples for most file types:

@example
/usr/local/bin/tex
/usr/local/man/man1/xdvi.1
/usr/local/info/kpathsea.info
/usr/local/lib/libkpathsea.a
/usr/local/share/texmf/bibtex/bst/base/plain.bst
/usr/local/share/texmf/fonts/pk/ljfour/public/cm/cmr10.600pk
/usr/local/share/texmf/fonts/source/public/pandora/pnr10.mf
/usr/local/share/texmf/fonts/tfm/public/cm/cmr10.tfm
/usr/local/share/texmf/fonts/type1/adobe/utopia/putr.pfa
/usr/local/share/texmf/metafont/base/plain.mf
/usr/local/share/texmf/metapost/base/plain.mp
/usr/local/share/texmf/tex/plain/base/plain.tex
/usr/local/share/texmf/tex/generic/hyphen/hyphen.tex
/usr/local/share/texmf/web2c/tex.pool
/usr/local/share/texmf/web2c/tex.fmt
/usr/local/share/texmf/web2c/texmf.cnf
@end example


@node Path searching
@chapter Path searching

@cindex path searching

This chapter describes the generic path searching mechanism Kpathsea
provides.  For information about searching for particular file types
(e.g., @TeX{} fonts), see the next chapter.

@cindex translations, of path searching description
This section, with minor differences, has been translated into several
other languages (Chinese, Spanish, Russian, Japanese, French, German,
@dots{}) as part of the @TeX{} Live guide; see
@url{https://tug.org/texlive/doc.html} for links.

@menu
* Searching overview::          Basic scheme for searching.
* Path sources::                Where search paths can be defined.
* Path expansion::              Special constructs in search paths.
* Casefolding search::          Fallback to case-insensitive search.
* Filename database::           Using an externally-built list to search.
* Invoking kpsewhich::          Standalone path lookup.
@end menu


@node Searching overview
@section Searching overview

@cindex searching overview
@cindex path searching, overview
@cindex overview of path searching

@cindex search path, defined
A @dfn{search path} is a colon-separated list of @dfn{path elements},
which are directory names with a few extra frills.  A search path can
come from (a combination of) many sources; see below.  To look up a file
@samp{foo} along a path @samp{.:/dir}, Kpathsea checks each element of
the path in turn: first @file{./foo}, then @file{/dir/foo}, returning
the first match (or possibly all matches).

@cindex magic characters
@kindex : @r{may not be :}
@kindex / @r{may not be /}
The ``colon'' and ``slash'' mentioned here aren't necessarily @samp{:}
and @samp{/} on non-Unix systems.  Kpathsea tries to adapt to other
operating systems' conventions.

@cindex database search
@cindex searching the database
To check a particular path element @var{e}, Kpathsea first sees if a
prebuilt database (@pxref{Filename database}) applies to @var{e}, i.e.,
if the database is in a directory that is a prefix of @var{e}.  If so,
the path specification is matched against the contents of the database.

@cindex floating directories
@cindex filesystem search
@cindex disk search
@cindex searching the disk
If the database does not exist, or does not apply to this path element,
or contains no matches, the filesystem is searched (if this was not
forbidden by the specification with @samp{!!} and if the file being
searched for must exist).  Kpathsea constructs the list of directories
that correspond to this path element, and then checks in each for the
file being searched for.  (To help speed future lookups of files in the
same directory, the directory in which a file is found is floated to the
top of the directory list.)

@cindex must exist
@cindex VF files, not found
@flindex cmr10.vf
@findex \openin
The ``file must exist'' condition comes into play with VF files and
input files read by the @TeX{} @samp{\openin} command.  These files
might very well not exist (consider @file{cmr10.vf}), and so it would
be wrong to search the disk for them.  Therefore, if you fail to
update @file{ls-R} when you install a new VF file, it will not be
found.

Each path element is checked in turn: first the database, then the
disk.  If a match is found, the search stops and the result is
returned (unless the search explicitly requested all matches).  This
avoids possibly-expensive processing of path specifications that are
never needed on a particular run.

On Unix-like systems, if no match is found by any of the above, and
the path element allows checking the filesystem (per the above), a
final check is made for a case-insensitive match. Thus, looking for a
name like @samp{./FooBar.TeX} will match a file @samp{./foobar.tex},
and vice versa.  This is not done on Windows.  @xref{Casefolding
search}.

@cindex expansion, path element
Although the simplest and most common path element is a directory name,
Kpathsea supports additional features in search paths: layered default
values, environment variable names, config file values, users' home
directories, and recursive subdirectory searching.  Thus, we say that
Kpathsea @dfn{expands} a path element, meaning transforming all the
magic specifications into the basic directory name or names.  This
process is described in the sections below.  It happens in the same
order as the sections.

@cindex absolute filenames
@cindex relative filenames
@cindex explicitly relative filenames
@cindex filenames, absolute or explicitly relative
Exception to all of the above: If the filename being searched for is
absolute or explicitly relative, i.e., starts with @samp{/} or @samp{./}
or @samp{../}, Kpathsea simply checks if that file exists, with a
fallback to a casefolding match if needed and enabled, as described above.

@cindex permission denied
@cindex unreadable files
@cindex access warnings
@cindex warnings, file access
@flindex lost+found @r{directory}
@vindex TEX_HUSH
Ordinarily, if Kpathsea tries to access a file or directory that
cannot be read, it gives a warning.  This is so you will be alerted to
directories or files that accidentally lack any read permission (for
example, a @file{lost+found} directory).  If you prefer not to see
these warnings, include the value @samp{readable} in the
@code{TEX_HUSH} environment variable or config file value.

This generic path searching algorithm is implemented in
@file{kpathsea/pathsearch.c}.  It is employed by a higher-level
algorithm when searching for a file of a particular type (@pxref{File
lookup}, and @ref{Glyph lookup}).


@node Path sources
@section Path sources

@cindex path sources
@cindex sources for search paths

A search path or other configuration value can come from many sources.
In the order in which Kpathsea looks for them:

@enumerate
@item
@opindex @samp{--cnf-line}, source for path
A command-line option such as @code{--cnf-line}, available in
@file{kpsewhich} and most @TeX{} engines.  @xref{Path searching
options}. 

@cindex environment variable, source for path
A user-set environment variable, e.g., @code{TEXINPUTS}.
Environment variables with an underscore and the program name appended
override; for example, @code{TEXINPUTS_latex} overrides @code{TEXINPUTS}
if the program being run is named @samp{latex}.

@item
A program-specific configuration file, e.g., an @samp{S /a:/b} line in
Dvips' @file{config.ps} (@pxref{Config files,,, dvips, Dvips}).

@item
@cindex configuration file, source for path
@cindex Kpathsea config file, source for path
@flindex texmf.cnf@r{, source for path}
A line in a Kpathsea configuration file @file{texmf.cnf}, e.g.,
@samp{TEXINPUTS=/c:/d} (see below).

@item
@cindex compilation value, source for path
The compile-time default (specified in @file{kpathsea/paths.h}).
@end enumerate

You can see each of these values for a given search path by using the
debugging options (@pxref{Debugging}).

These sources may be combined via default expansion (@pxref{Default
expansion}).

@menu
* Config files::        Kpathsea's runtime config files (texmf.cnf).
@end menu


@node Config files
@subsection Config files

@cindex config files
@flindex texmf.cnf@r{, definition for}

@cindex runtime configuration files
@vindex TEXMFCNF
As mentioned above, Kpathsea reads @dfn{runtime configuration files}
named @file{texmf.cnf} for search path and other definitions.  The
search path used to look for these configuration files is named
@code{TEXMFCNF}, and is constructed in the usual way, as described
above, except that configuration files cannot be used to define the
path, naturally; also, an @file{ls-R} database is not used to search for
them.

Kpathsea reads @emph{all} @file{texmf.cnf} files in the search path, not
just the first one found; definitions in earlier files override those in
later files.  Thus, if the search path is @samp{.:$TEXMF}, values from
@file{./texmf.cnf} override those from @file{$TEXMF/texmf.cnf}.

@vindex KPATHSEA_WARNING
@cindex warning, about missing @file{texmf.cnf}
@cindex @file{texmf.cnf} missing, warning about
If Kpathsea cannot find any @file{texmf.cnf} file, it reports a
warning including all the directories it checked.  If you don't want
to see this warning, set the environment variable
@env{KPATHSEA_WARNING} to the single character @samp{0} (zero, not
oh).

While (or instead of) reading this description, you may find it helpful
to look at the distributed @file{texmf.cnf}, which uses or at least
mentions most features.  The format of @file{texmf.cnf} files follows:

@itemize @bullet
@item
@cindex comments, in @file{texmf.cnf}
Comments start with @samp{%} or @samp{#}, either at the beginning of a
line or preceded by whitespace, and continue to the end of the line.
That is, similar to most shells, a comment character in the ``middle''
of a value does not start a comment.  Examples:

@example
% this is a comment
var = a%b  % but the value of var will be "a%b"
@end example

@item
@cindex blank lines, in @file{texmf.cnf}
Blank lines are ignored.

@item
@cindex backslash-newline
@cindex continuation character
@cindex whitespace, not ignored on continuation lines
@kindex \@r{, line continuation in @file{texmf.cnf}}
A @samp{\} at the end of a line acts as a continuation character, i.e.,
the next line is appended.  Whitespace at the beginning of continuation
lines is not ignored.

@item Each remaining line will look like:

@example
@var{variable} @r{[}. @var{progname}@r{]} @r{[}=@r{]} @var{value}
@end example

@noindent where the @samp{=} and surrounding whitespace is optional.

@item
@cindex identifiers, characters valid in
The @var{variable} name may contain any character other than whitespace,
@samp{=}, or @samp{.}, but sticking to @samp{A-Za-z_} is safest.

@kindex .@var{progname} @r{qualifier in @file{texmf.cnf}}
@item If @samp{.@var{progname}} is present (preceding spaces are
ignored), the definition only applies if the program that is running
is named (i.e., the last component of @code{argv[0]} is)
@var{progname} or @file{@var{progname}.@{exe,bat,cmd,...@}}.  Most
notably, this allows different flavors of @TeX{} to have different
search paths.  The @var{progname} value is used literally, without
variable or other expansions.

@item
@cindex right-hand side of variable assignments
Considered as strings, @var{value} may contain any character.
However, in practice most @file{texmf.cnf} values are related to path
expansion, and since various special characters are used in expansion,
such as braces and commas, they cannot be used in directory names.
  
The @samp{$@var{var}.@var{prog}} feature is not available on the
right-hand side; instead, you must use an additional variable (see
below for example).

@kindex ; @r{translated to @samp{:} in @file{texmf.cnf}}
A @samp{;} in @var{value} is translated to @samp{:} if running under
Unix, in order to have a single @file{texmf.cnf} that can support both
Unix and Windows systems. This translation happens with any value, not
just search paths, but fortunately in practice @samp{;} is not needed
in other values.

@item All definitions are read before anything is expanded, so you can
use variables before they are defined (like Make, unlike most other
programs).
@end itemize

@noindent Here is a configuration file fragment illustrating most of
these points:

@example
% TeX input files -- i.e., anything to be found by \input or \openin ...
latex209_inputs = .:$TEXMF/tex/latex209//:$TEXMF/tex//
latex2e_inputs = .:$TEXMF/tex/latex//:$TEXMF/tex//
TEXINPUTS = .:$TEXMF/tex//
TEXINPUTS.latex209 = $latex209_inputs
TEXINPUTS.latex2e = $latex2e_inputs
TEXINPUTS.latex = $latex2e_inputs
@end example

@kindex = @r{omitted in @file{texmf.cnf} and misparsing}
The combination of spaces being ignored before the @code{.} of a
program name qualifer and the optional @samp{=} for the assignment has
an unexpected consequence: if the value begins with a literal @samp{.}
and the @samp{=} is omitted, the intended value is interpreted as a
program name.  For example, a line @code{var .;/some/path} is taken as
an empty value for @code{var} running under the program named
@samp{;/some/path}.  To diagnose this, Kpathsea warns if the program
name contains a path separator or other special character.  The
simplest way to avoid the problem is to use the @code{=}.

Exactly when a character will be considered special or act as itself
depends on the context in which it is used. The rules are inherent in
the multiple levels of interpretation of the configuration (parsing,
expansion, search, @dots{}) and so cannot be concisely stated,
unfortunately. There is no general escape mechanism; in particular,
@samp{\} is not an ``escape character'' in @file{texmf.cnf} files.
When it comes choosing directory names for installation, it is safest to
avoid them all.

@flindex cnf.c
The implementation of all this is in @file{kpathsea/cnf.c}.


@node Path expansion
@section Path expansion

@cindex path expansion
@cindex expansion, search path

Kpathsea recognizes certain special characters and constructions in
search paths, similar to that in shells.  As a general example:
@samp{~$USER/@{foo,bar@}//baz} expands to all subdirectories under
directories @file{foo} and @file{bar} in @t{$USER}'s home directory that
contain a directory or file @file{baz}.

These expansions are explained in the sections below.

@menu
* Default expansion::           a: or :a or a::b expands to a default.
* Variable expansion::          $foo and $@{foo@} expand to environment values.
* Tilde expansion::             ~ and ~user expand to home directories.
* Brace expansion::             a@{foo,bar@}b expands to afoob abarb.
* KPSE_DOT expansion::          . is replaced with $KPSE_DOT if it is defined.
* Subdirectory expansion::      a// and a//b recursively expand to subdirs.
@end menu


@node Default expansion
@subsection Default expansion

@kindex :: @r{expansion}
@cindex doubled colons
@cindex leading colons
@cindex trailing colons
@cindex extra colons
@cindex default expansion
@cindex expansion, default

If the highest-priority search path (@pxref{Path sources}) contains an
@dfn{extra colon} (i.e., leading, trailing, or doubled), Kpathsea
inserts at that point the next-highest-priority search path that is
defined.  If that inserted path has an extra colon, the same happens
with the next-highest.  (An extra colon in the compile-time default
value has unpredictable results, so installers beware.)

For example, given an environment variable setting

@example
setenv TEXINPUTS /home/karl:
@end example

@noindent and a @code{TEXINPUTS} value from @file{texmf.cnf} of

@example
.:$TEXMF//tex
@end example

@noindent then the final value used for searching will be:

@example
/home/karl:.:$TEXMF//tex
@end example

Put another way, default expansion works on ``formats'' (search
paths), and not directly on environment variables.  Example, showing
the trailing @samp{:} ignored in the first case and expanded in the second:

@example
$ env TTFONTS=/tmp: kpsewhich --expand-path '$TTFONTS'
/tmp
$ env TTFONTS=/tmp: kpsewhich --show-path=.ttf
/tmp:.:/home/olaf/texmf/fonts/truetype//:...
@end example

Since Kpathsea looks for multiple configuration files, it would be
natural to expect that (for example) an extra colon in
@file{./texmf.cnf} would expand to the path in @file{$TEXMF/texmf.cnf}.
Or, with Dvips' configuration files, that an extra colon in
@file{config.$PRINTER} would expand to the path in @file{config.ps}.
This doesn't happen.  It's not clear this would be desirable in all
cases, and trying to devise a way to specify the path to which the extra
colon should expand seemed truly baroque.
@cindex Bach, Johann Sebastian

Technicality: Since it would be useless to insert the default value in
more than one place, Kpathsea changes only one extra @samp{:} and leaves
any others in place (they will eventually be ignored).  Kpathsea checks
first for a leading @samp{:}, then a trailing @samp{:}, then a doubled
@samp{:}.

@flindex kdefault.c
You can trace this by debugging ``paths'' (@pxref{Debugging}).
Default expansion is implemented in the source file
@file{kpathsea/kdefault.c}.


@node Variable expansion
@subsection Variable expansion

@kindex $ @r{expansion}
@cindex environment variables in paths
@cindex variable expansion
@cindex expansion, variable
@flindex texmf.cnf@r{, and variable expansion}

@samp{$foo} or @samp{$@{foo@}} in a path element is replaced by (1) the
value of an environment variable @samp{foo} (if defined); (2) the value
of @samp{foo} from @file{texmf.cnf} (if defined); (3) the empty string.

If the character after the @samp{$} is alphanumeric or @samp{_}, the
variable name consists of all consecutive such characters. If the
character after the @samp{$} is a @samp{@{}, the variable name consists
of everything up to the next @samp{@}} (braces may not be nested around
variable names).  Otherwise, Kpathsea gives a warning and ignores the
@samp{$} and its following character.

@cindex quoting variable values
@cindex shell variables
You must quote the @t{$}'s and braces as necessary for your shell.
@emph{Shell} variable values cannot be seen by Kpathsea, i.e., ones
defined by @code{set} in C shells and without @code{export} in Bourne
shells.

For example, given
@example
setenv tex /home/texmf
setenv TEXINPUTS .:$tex:$@{tex@}prev
@end example
@noindent the final @code{TEXINPUTS} path is the three directories:
@example
.:/home/texmf:/home/texmfprev
@end example

The @samp{.@var{progname}} suffix on variables and
@samp{_@var{progname}} on environment variable names are not implemented
for general variable expansions.  These are only recognized when search
paths are initialized (@pxref{Path sources}).

@flindex variable.c
Variable expansion is implemented in the source file
@file{kpathsea/variable.c}.


@node Tilde expansion
@subsection Tilde expansion

@kindex ~ @r{expansion}
@cindex home directories in paths
@cindex tilde expansion
@cindex expansion, tilde

@vindex HOME@r{, as ~ expansion}
@vindex USERPROFILE@r{, as ~ expansion}
A leading @samp{~} in a path element is replaced by the value of the
environment variable @code{HOME}, or @file{.} if @code{HOME} is not
set.  On Windows, the environment variable @code{USERPROFILE} is
checked instead of @code{HOME}.

A leading @samp{~@var{user}} in a path element is replaced by
@var{user}'s home directory from the system @file{passwd} database.

For example,
@example
setenv TEXINPUTS ~/mymacros:
@end example

@noindent will prepend a directory @file{mymacros} in your home
directory to the default path.

@cindex @t{root} user
@cindex trailing @samp{/} in home directory
@kindex /@r{, trailing in home directory}
As a special case, if a home directory ends in @samp{/}, the trailing
slash is dropped, to avoid inadvertently creating a @samp{//} construct
in the path.  For example, if the home directory of the user @samp{root}
is @samp{/}, the path element @samp{~root/mymacros} expands to just
@samp{/mymacros}, not @samp{//mymacros}.

@flindex tilde.c
Tilde expansion is implemented in the source file @file{kpathsea/tilde.c}.


@node Brace expansion
@subsection Brace expansion

@kindex @{ @r{expansion}
@cindex brace expansion

@samp{x@{@var{a},@var{b}@}y} expands to @samp{x@var{a}y:x@var{b}y}.
For example:

@example
foo/@{1,2@}/baz
@end example

@noindent expands to @samp{foo/1/baz:foo/2/baz}.  @samp{:} is the path
separator on the current system; e.g., on a Windows system, it's @samp{;}.

Braces can be nested; for example, @samp{x@{A,B@{1,2@}@}y} expands to
@samp{xAy:xB1y:xB2y}.

Multiple non-nested braces are expanded from right to left; for example,
@samp{x@{A,B@}@{1,2@}y} expands to @samp{x@{A,B@}1y:x@{A,B@}2y}, which
expands to @samp{xA1y:xB1y:xA2y:xB2y}.

@cindex multiple @TeX{} hierarchies
This feature can be used to implement multiple @TeX{} hierarchies, by
assigning a brace list to @code{$TEXMF}, as mentioned in
@file{texmf.in}.

You can also use the path separator instead of the comma.  The last
example could have been written @samp{x@{A:B@}@{1:2@}y} (on Unix).


@flindex expand.c
Brace expansion is implemented in the source file
@file{kpathsea/expand.c}.


@node KPSE_DOT expansion
@subsection @code{KPSE_DOT} expansion

@kindex KPSE_DOT @r{expansion}

When @code{KPSE_DOT} is defined in the environment, it names a directory
that should be considered the current directory for the purpose of
looking up files in the search paths.  This feature is needed by the
@samp{mktex@dots{}} scripts @ref{mktex scripts}, because these
change the working directory.  You should not ever define it yourself.


@node Subdirectory expansion
@subsection Subdirectory expansion

@kindex //
@cindex subdirectory searching
@cindex expansion, subdirectory

@cindex alphabetical order, not
Two or more consecutive slashes in a path element following a directory
@var{d} is replaced by all subdirectories of @var{d}: first those
subdirectories directly under @var{d}, then the subsubdirectories under
those, and so on.  At each level, the order in which the directories are
searched is unspecified.  (It's ``directory order'', and definitely not
alphabetical.)

If you specify any filename components after the @samp{//}, only
subdirectories which match those components are included.  For example,
@samp{/a//b} would expand into directories @file{/a/1/b}, @file{/a/2/b},
@file{/a/1/1/b}, and so on, but not @file{/a/b/c} or @file{/a/1}.

You can include multiple @samp{//} constructs in the path.

@samp{//} at the beginning of a path is ignored.  Searching every
directory on the system is not relevant for @TeX{}.

@cindex trick for detecting leaf directories
@cindex leaf directory trick
@cindex Farwell, Matthew
@cindex MacKenzie, David
We need to discuss one related implementation trick, originally taken
from GNU find.  Matthew Farwell suggested it, and David MacKenzie
implemented it.

@vindex st_nlink
The trick is that in normal Unix implementations (though not in the
POSIX specification), a directory which contains no subdirectories
will have exactly two links (namely, one for @file{.} and one for
@file{..}).  That is to say, the @code{st_nlink} field in the
@samp{stat} structure will be two.  Thus, we don't have to stat
everything in the bottom-level (leaf) directories---we can just check
@code{st_nlink}, notice it's two, and do no more work.

Kpathsea never does this @code{st_nlink=2} check (or any disk
checking) for @code{!!} trees (@pxref{ls-R}).  And the non-@code{!!}
trees in a @TeX{} Live installation are typically extremely small.
Therefore the @code{st_nlink} check is not performed by default at
all, as of 2025 (Kpathsea 6.3.4). That way, two not-uncommon
situations work out: 1)@tie{}all @code{gvisor}-handled filesystems return
@code{st_nlink=1} before some post-2025 release
(@url{https://tug.org/pipermail/texhax/2025-July/026772.html});
2)@tie{}a symbolic link to another directory in such an apparent leaf
directory will get followed even though @code{st_nlink=2} 
(@url{https://tex.stackexchange.com/questions/132908}).

If you have an extremely large non-@code{!!} tree, most likely
@code{TEXMFHOME}, you may find it useful to enable the check: you can
do this by setting the configuration variable
@code{texmf_nlink_for_leaf} to 1. Alternatively, with such a large
tree, you may find it even more useful to add the tree to
@code{TEXMFDBS} so that only @code{ls-R} lookups are done (again,
@pxref{ls-R}).

@flindex elt-dirs.c
Unfortunately, in some cases files in leaf directories are
@code{stat}'d anyway: if the path specification is, say,
@samp{$TEXMF/fonts//pk//}, then files in a subdirectory
@samp{@dots{}/pk}, even if it is a leaf, are checked. The reason
cannot be explained without reference to the implementation, so read
@file{kpathsea/elt-dirs.c} (search for @samp{may descend}) if you are
curious.  And if you find a way to solve the problem, please let me
know.

@flindex elt-dirs.c
Subdirectory expansion is implemented in the source file
@file{kpathsea/elt-dirs.c}.


@node Casefolding search
@section Casefolding search

@cindex casefolding search
@cindex search, case-insensitive

In Kpathsea version 6.3.0 (released with @TeX{} Live 2018), a new
fallback search was implemented on Unix-like systems, including Macs:
for each path element in turn, if no match is found by the normal
search, and the path element allows for checking the filesystem, a
second check is made for a case-insensitive match.

@vindex texmf_casefold_search
This is enabled at compile-time on Unix systems, and enabled at
runtime by setting the configuration variable
@code{texmf_casefold_search}, to a true value, e.g., @samp{1}; this is
done by default in @TeX{} Live.

@menu
* Rationale: Casefolding rationale.
* Examples: Casefolding examples.
@end menu

@node Casefolding rationale
@subsection Casefolding rationale

@cindex casefolding fallback rationale
@cindex rationale for casefolding fallback
@cindex system-dependent casefolding behavior

@cindex filesystem, case-(in)sensitive
@cindex Apple filesystem, case-insensitive
@cindex Mac filesystem, case-insensitive
The purpose of the fallback casefolding search is to ease moving
complex documents between case-insensitive (file)systems and
case-sensitive ones.  In particular, Apple decided to make the default
filesystem on Macs be case-insensitive some years ago, and this has
exacerbated a problem of people creating documents that use, say, an
image under the name @file{foo.jpg}, while the actual file is named
@file{foo.JPG} or @file{Foo.jpg}. It works on the Mac but if the
document is transferred and run on a standard case-sensitive Unix
(file)system, the file can't be found, due only to differences in
case.

This same problematic scenario has always existed on Windows, but for
whatever reason, it has become much more common since Apple also went
to a case-insensitive filesystem.  Hence the relatively late change
to the Kpathsea behavior.

@cindex Windows and casefolding
The fallback case-insensitive search is omitted at compile-time on
Windows, where (for practical purposes) all file names are
case-insensitive at the kernel level, and so the normal search will
already have definitively matched or not.  Therefore, search results
in unusual cases can be different on Windows and Unix---but this has
always been true.


@node Casefolding examples
@subsection Casefolding examples

@cindex casefolding examples
@cindex examples, of casefolding searches

The casefolding implementation prefers exact matches to casefolded
matches within a given path element, so as to retain most
compatibility.  Backward compatibility is not perfect, however, as a
casefolded match may be found in an earlier path element than an exact
match was previously found (see example #4 below).  Still, preferring
the match in the earlier element seemed potentially less confusing
than otherwise, and is in fact consistent with past behavior on
Windows.  Since case mismatches are rare to begin with, and name
collisions with respect only to case thus even more rare, the hope is
that it will not cause difficulties in practice.

If it's desirable in a given situation to have the exact same search
behavior as previously, that can be accomplished by setting the
configuration variable @code{texmf_casefold_search} to @samp{0}
(@pxref{Path sources}).

Some examples to illustrate the new behavior follow.

Example #1: suppose the file @file{./foobar.tex} exists. Now,
searching for @file{./FooBar.TeX} (or any other case variation) will
succeed, returning @file{./foobar.tex}---the name as stored on disk.
In previous releases, or if @code{texmf_casefold_search} is false, the
search would fail.

Example #2: suppose we are using a case-sensitive (file)system, and
the search path is @samp{.:/somedir}, and the files
@file{./foobar.tex} and @file{/somedir/FooBar.TeX} both exist.  Both
now and previously, searching for @file{foobar.tex} returns
@file{./foobar.tex}.  However, searching for @file{FooBar.TeX} now
returns @file{./foobar.tex} instead of @file{/somedir/FooBar.TeX};
this is the incompatibility mentioned above.  Also (as expected),
searching for @file{FOOBAR.TEX} (or whatever variation) will now
return @file{./foobar.tex}, whereas before it would fail.  Searching
for all (@samp{kpsewhich --all}) @file{foobar.tex} will return both
matches.

Example #3: same as example #2, but on a case-insensitive
(file)system: both now and previously, searching for @file{FooBar.TeX}
returns @file{./foobar.tex}, since the system considers that a match.
The Kpathsea casefolding never comes into play.

Example #4: if we have (on a case-sensitive system) both
@file{./foobar.tex} and @file{./FOOBAR.TEX}, searching with the exact
case returns that exact match, now and previously.  Searching for
@file{FooBar.tex} will now return one or the other (chosen
arbitrarily), rather than failing.  Perhaps unexpectedly, searching
for all @file{foobar.tex} or @file{FooBar.tex} will also return only
one or the other, not both (see more below).

Example #5: the font file @file{STIX-Regular.otf} is included in
@TeX{} Live in the system directory
@file{texmf-dist/fonts/opentype/public/stix}.  Because Kpathsea never
searches the disk in the big system directory, the casefolding is not
done, and a search for @samp{stix-regular.otf} will fail (on
case-sensitive systems), as it always has.

@kindex !! @r{and casefolding}
The caveat about not searching the disk amounts to saying that
casefolding does not happen in the trees specified with @samp{!!}
(@pxref{ls-R}), that is, where only database (@file{ls-R}) searching
is done.  In @TeX{} Live, that is the @samp{texmf-local} and
@samp{texmf-dist} trees (also @code{$TEXMFSYSCONFIG} and
@code{$TEXMFSYSVAR}, but those are rarely noticed).  The rationale for
this is that in practice, case mangling happens with user-created
files, not with packages distributed as part of the @TeX{} system.

One more caveat: the purpose of @code{kpsewhich} is to exercise the
path searching in Kpathsea as it is actually done.  Therefore, as
shown above, @samp{kpsewhich --all} will not return all matches
regardless of case within a given path element.  If you want to find
all matches in all directories, @code{find} is the best tool, although
the setup takes a couple steps:

@example
kpsewhich -show-path=tex >/tmp/texpath      # search path specification
kpsewhich -expand-path="`cat /tmp/texpath`" >/tmp/texdirs  # all dirs
tr ':' '\n' </tmp/texdirs >/tmp/texdirlist  # colons to newlines
find `cat /tmp/texdirlist` -iname somefile.tex -print </tmp/texdirlist
@end example

@cindex Findutils, GNU package
@opindex -iname@r{, find predicate}
Sorry that it's annoyingly lengthy, but implementing this inside
Kpathsea would be a lot of error-prone trouble for something that is
only useful for debugging.  If your @code{find} does not support
@code{-iname}, you can get GNU Find from
@url{https://gnu.org/software/findutils}.

The casefolding search is implemented in the source file
@file{kpathsea/pathsearch.c}.  Two implementation points:

@itemize
@findex access @r{system call}
@item
Kpathsea never tries to check if a given directory resides on a
case-insensitive filesystem, because there is no efficient and
portable way to do so.  All it does is try to see if a potential file
name is a readable normal file (with, usually, the @code{access}
system call).

@item
Kpathsea does not do any case-insensitive matching of the directories
along the path.  It's not going to find @file{/Some/Random/file.tex}
when looking for @file{/some/random/file.tex}.  The casefolding only
happens with the elements of the leaf directory.

@end itemize


@node Filename database
@section Filename database (@code{ls-R})

@cindex filename database
@cindex database, for filenames
@cindex externally-built filename database

Kpathsea goes to some lengths to minimize disk accesses for searches
(@pxref{Subdirectory expansion}).  Nevertheless, in practice searching
every possible directory in typical @TeX{} installations takes an
excessively long time.

Therefore, Kpathsea can use an externally-built @dfn{filename
database} file named @file{ls-R} that maps files to directories, thus
avoiding the need to exhaustively search the disk.

A second database file @file{aliases} allows you to give additional
names to the files listed in @file{ls-R}.

The @file{ls-R} and @file{aliases} features are implemented in the
source file @file{kpathsea/db.c}.

@menu
* ls-R::                        The main filename database.
* Filename aliases::            Aliases for those names.
* Database format::             Syntax details of the database file.
@end menu


@node ls-R
@subsection @file{ls-R}

@flindex ls-R @r{database file}

As mentioned above, you must name the main filename database
@file{ls-R}.  You can put one at the root of each @TeX{} installation
hierarchy you wish to search (@code{$TEXMF} by default, which expands
to a braced list of several hierarchies in @TeX{} Live). 

@vindex TEXMFDBS
@kindex !! @r{in @code{TEXMFDBS}}
Kpathsea looks for @file{ls-R} files along the @code{TEXMFDBS}
path. It is best for this to contain all and only those hierarchies
from @code{$TEXMF} which are specified with @code{!!}---and also to
specify them with @code{!!} in @code{TEXMFDBS}. (See the end of this
section for more on @code{!!}.)

The recommended way to create and maintain @samp{ls-R} is to run the
@code{mktexlsr} script, which is installed in @samp{$(bindir)}
(@file{/usr/local/bin} by default).  That script goes to some trouble to
follow symbolic links as necessary, etc.  It's also invoked by the
distributed @samp{mktex@dots{}} scripts.

@flindex ls-R@r{, simplest build}
At its simplest, though, you can build @file{ls-R} with the command
@example
cd @var{/your/texmf/root} && ls -LAR ./ >ls-R
@end example

@noindent
@opindex --color=tty
@flindex /etc/profile @r{and aliases}
presuming your @code{ls} produces the right output format (see the
section below).  GNU @code{ls}, for example, outputs in this format.
Also presuming your @code{ls} hasn't been aliased in a system file
(e.g., @file{/etc/profile}) to something problematic, e.g., @samp{ls
--color=tty}.  In that case, you will have to disable the alias before
generating @file{ls-R}.  For the precise definition of the file format,
see @ref{Database format}.

Regardless of whether you use the supplied script or your own, you
will almost certainly want to invoke it via @code{cron}, so when you
make changes in the installed files (say if you install a new @LaTeX{}
package), @file{ls-R} will be automatically updated.  However, for
those using @TeX{} Live or system distributions, the package managers
should run @code{mktexlsr} as needed.

@opindex -A @r{option to @code{ls}}
@cindex dot files
@flindex . @r{files}
@flindex . @r{directories, ignored}
@flindex .tex @r{file, included in @file{ls-R}}
The @samp{-A} option to @code{ls} includes files beginning with @samp{.}
(except for @file{.} and @file{..}), such as the file @file{.tex}
included with the @LaTeX{} tools package.  (On the other hand,
@emph{directories} whose names begin with @samp{.} are always ignored.)

@cindex symbolic links, and @file{ls-R}
@opindex -L @r{option to @code{ls}}
If your system does not support symbolic links, omit the @samp{-L}.

@cindex automounter, and @file{ls-R}
@cindex NFS and @file{ls-R}
@code{ls -LAR @var{/your/texmf/root}} will also work.  But using
@samp{./} avoids embedding absolute pathnames, so the hierarchy can be
easily transported.  It also avoids possible trouble with automounters
or other network filesystem conventions.

@cindex warning about unusable @file{ls-R}
@cindex unusable @file{ls-R} warning
Kpathsea warns you if it finds an @file{ls-R} file, but the file does
not contain any usable entries.  The usual culprit is running plain
@samp{ls -R} instead of @samp{ls -LR ./} or @samp{ls -R
@var{/your/texmf/root}}.  Another possibility is some system directory
name starting with a @samp{.} (perhaps if you are using AFS); Kpathsea
ignores everything under such directories.

@kindex !! @r{in path specifications}
@cindex disk searching, avoiding
If a particular path element begins with @samp{!!}, @emph{only} the
database will be searched for that element, never the disk; and if the
database does not exist, nothing at all will be searched.  In @TeX{}
Live, most of the trees are specified with @samp{!!}.

For path elements that do not begin with @samp{!!}, if the database
exists, it will be used, and the disk will not be searched.  However,
in this case, if the database does not exist, the disk will be
searched.  In @TeX{} Live, the most notable case of this is the
@code{TEXMFHOME} tree, to allow users to add and remove files from
their own tree without having to worry about @code{ls-R}.

(Aside: there are uncommon cases where a @samp{!!} tree will be
searched on disk even if the @code{ls-R} file exists; they are too
obscure to try to explain here.  See @file{pathsearch.c} in the source
if you need to know.)

To sum up: do not create an @code{ls-R} file unless you also take care
to keep it up to date. Otherwise newly-installed files will not be
found.



@node Filename aliases
@subsection Filename aliases

@cindex filename aliases
@cindex aliases, for filenames

In some circumstances, you may wish to find a file under several names.
For example, suppose a @TeX{} document was created using a DOS system
and tries to read @file{longtabl.sty}.  But now it's being run on a Unix
system, and the file has its original name, @file{longtable.sty}.  The
file won't be found.  You need to give the actual file
@file{longtable.sty} an alias @samp{longtabl.sty}.

@c As another example, suppose you are creating a @TeX{} distribution on a
@c CD-ROM or a DOS system; then the file @file{mf.base} gets stored as
@c @file{mf.bas}.  But Metafont on Unix wants to find @file{mf.base}.  Here
@c you need to give the actual file @file{mf.bas} an alias @samp{mf.base}.

You can handle this by creating a file @file{aliases} as a companion to
the @file{ls-R} for the hierarchy containing the file in question.  (You
must have an @file{ls-R} for the alias feature to work.)

The format of @file{aliases} is simple: two whitespace-separated words
per line; the first is the real name @file{longtable.sty}, and second is
the alias (@file{longtabl.sty}).  These must be base filenames, with no
directory components.  @file{longtable.sty} must be in the sibling
@file{ls-R}.

Also, blank lines and lines starting with @samp{%} or @samp{#} are
ignored in @file{aliases}, to allow for comments.

If a real file @file{longtabl.sty} exists, it is used regardless of any
aliases.


@node Database format
@subsection Database format

@cindex format of external database
@cindex database, format of

The ``database'' read by Kpathsea is a line-oriented file of plain
text. The format is that generated by GNU (and most other) @code{ls}
programs given the @samp{-R} option, as follows.

@itemize @bullet
@item
Blank lines are ignored.

@item
If a line begins with @samp{/} or @samp{./} or @samp{../} and ends with
a colon, it's the name of a directory.  (@samp{../} lines aren't useful,
however, and should not be generated.)

@item
All other lines define entries in the most recently seen directory.
@t{/}'s in such lines will produce possibly-strange results.

@item
Files with no preceding directory line are ignored.
@end itemize

For example, here's the first few lines of @file{ls-R} (which totals
about 30K bytes) on my system:

@example
bibtex
dvips
fonts
ls-R
metafont
metapost
tex
web2c

./bibtex:
bib
bst
doc

./bibtex/bib:
asi.bib
btxdoc.bib
@dots{}
@end example


@node Invoking kpsewhich
@section @code{kpsewhich}: Standalone path searching

@pindex kpsewhich
@cindex path searching, standalone
@cindex standalone path searching

The Kpsewhich program exercises the path searching functionality
independent of any particular application.  This can also be useful as a
sort of @code{find} program to locate files in your @TeX{} hierarchies,
perhaps in administrative scripts.  It is used heavily in the
distributed @samp{mktex@dots{}} scripts.

Synopsis:

@example
kpsewhich @var{option}@dots{} @var{filename}@dots{}
@end example

The options and filename(s) to look up can be intermixed.
Options can start with either @samp{-} or @samp{--}, and any unambiguous
abbreviation is accepted.

Kpsewhich looks up each non-option argument on the command line as a
filename, and outputs (by default) the first file found to standard
output. If a file is not found, and more than @var{filename} is given,
a blank line is output for that file. See examples below.

The exit status is zero if all files were found, nonzero otherwise.

@menu
* kpsewhich examples::          Simple examples of running kpsewhich.
* Path searching options::      Changing the mode, resolution, etc.
* Specially-recognized files::  Default formats for texmf.cnf, etc.
* Auxiliary tasks::             Path and variable expansion, etc.
* Standard options::            @samp{--help} and @samp{--version}.
@end menu


@node kpsewhich examples
@subsection @code{kpsewhich} examples

@cindex @code{kpsewhich} examples
@cindex examples, of running @code{kpsewhich} 

Some examples of running @code{kpsewhich} with a typical @TeX{} tree.
A basic successful search (exit status 0):

@example
$ kpsewhich plain.tex
/usr/local/texlive/2024/texmf-dist/tex/plain/base/plain.tex
@end example

Searching for multiple files, one of which is not found (exit status
is 1 for this):

@example
$ kpsewhich plain.tex foobar plain.mf
/usr/local/texlive/2024/texmf-dist/tex/plain/base/plain.tex

/usr/local/texlive/2024/texmf-dist/metafont/base/plain.mf
@end example

Using @code{--all} to see all files by the same name (exit status 0):

@example
$ kpsewhich --all language.dat
/usr/local/texlive/2024/texmf-dist/tex/generic/config/language.dat
/usr/local/texlive/2024/texmf-dist/lambda/generic/config/language.dat
@end example

@node Path searching options
@subsection Path searching options

@cindex path searching options

Various options alter the path searching behavior. Options apply to
all lookups.

@table @samp
@item --all
@opindex --all
@cindex all matches, finding
Report all matches found, one per line.  By default, if there is more
than one match, just one will be reported (chosen effectively at
random).  Exception: with the glyph formats (@code{pk}, @code{gf}),
this option has no effect and only the first match is returned.

With both @code{-all} and multiple input files, there's no easy way to
discern which matches belong to which files; you have to check the
basename of the output.  This could be improved, if there is any demand.

@item --casefold-search
@itemx --no-casefold-search
@opindex --casefold-search
@opindex --no-casefold-search
Explicitly enable or disable the fallback to a case-insensitive search
on Unix platforms (@pxref{Casefolding search}); no effect on Windows.
The default is enabled, set in @code{texmf.cnf}.  Disabling
(@code{--no-casefold-search}) does not mean that searches magically
become case-sensitive when the underlying (file)system is
case-insensitive, it merely means that Kpathsea does not do any
casefolding itself.

@item --cnf-line=@var{str}
@opindex --cnf-line
Parse @var{str} as if it were a line in the @file{texmf.cnf}
configuration file (@pxref{Config files}), overriding settings in the
actual configuration files, and also in the environment (@pxref{Path
sources}).  This is implemented by making any settings from @var{str}
in the environment, overwriting any value already there.  Thus, an
extra colon in a @samp{--cnf-line} value will refer to the value from
a configuration file, not a user-set environment variable.

Furthermore, any variable set from @var{str} will also be set with the
program name suffix.  For example, @code{pdftex
--cnf-line=TEXINPUTS=/foo:} will set both @code{TEXINPUTS} and
@code{TEXINPUTS_pdftex} in the environment (and the value will be
@file{/foo} followed by the setting from @file{texmf.cnf}, ignoring
any user-set @code{TEXINPUTS}).

This behavior is desirable because, in practice, many variables in the
distributed @file{texmf.cnf} are program-specific, and the intuitive
behavior is for values set on the command line with @code{--cnf-line}
to override them.

@item --dpi=@var{num}
@opindex --dpi=@var{num}
@opindex -D @var{num}
@cindex resolution, setting
Set the resolution to @var{num}; this only affects @samp{gf} and
@samp{pk} lookups.  @samp{-D} is a synonym, for compatibility with
Dvips.  Default is 600.

@item --engine=@var{name}
@opindex --engine=@var{name}
@cindex engine name
Set the engine name to @var{name}.  By default it is not set in
@code{kpsewhich} (@TeX{} engines set it to the appropriate string).
The engine name is used in some search paths to allow files with the
same name but used by different engines to coexist.

In particular, since the memory dump files
(@file{.fmt}/@file{.base}/@file{.mem}) are now stored in
subdirectories named for the engine (@file{tex}, @file{pdftex},
@file{xetex}, etc.), you must specify an engine name in order to find
them.  For example, @file{cont-en.fmt} typically exists for both
@file{pdftex} and @file{xetex}.  With the default path settings, you
can use @samp{--engine=/} to look for any dump file, regardless of
engine; if a dump file exists for more than one engine, it's
indeterminate which one is returned.  (The @samp{/} ends up specifying
a normal recursive search along the path where the dumps are stored,
namely @samp{$TEXMF/web2c@{/$engine,@}}.)

@item --format=@var{name}
@opindex --format=@var{name}
Set the format for lookup to @var{name}.  By default, the format is
guessed from the filename, with @samp{tex} being used if nothing else
fits.  The recognized filename extensions (including any leading
@samp{.}) are also allowable @var{name}s.

All formats also have a name, which is the only way to specify formats
with no associated suffix.  For example, for Dvips configuration files
you can use @samp{--format="dvips config"}.  (The quotes are for the
sake of the shell.)

Here's the current list of recognized names and the associated suffixes.
@xref{Supported file formats}, for more information on each of these.

The strings in parentheses are abbreviations recognized only by
@code{kpsewhich} (not the underlying library calls).  They are
provided when it would otherwise require an argument containing a
space to specify the format, to simplify quoting of calls from shells.

@example
gf: gf
pk: pk
bitmap font (bitmapfont):
tfm: .tfm
afm: .afm
base: .base
bib: .bib
bst: .bst
cnf: .cnf
ls-R: ls-R ls-r
fmt: .fmt
map: .map
mem: .mem
mf: .mf
mfpool: .pool
mft: .mft
mp: .mp
mppool: .pool
MetaPost support (mpsupport):
ocp: .ocp
ofm: .ofm .tfm
opl: .opl  .pl
otp: .otp
ovf: .ovf .vf
ovp: .ovp  .vpl
graphic/figure:  .eps .epsi
tex: .tex  .sty .cls .fd .aux .bbl .def .clo .ldf
TeX system documentation (doc):
texpool: .pool
TeX system source (source, src):  .dtx .ins
PostScript header (psheader):  .pro
Troff fonts (trofffont):
type1 fonts: .pfa .pfb
vf: .vf
dvips config (dvipsconfig):
ist: .ist
truetype fonts (truetype, ttf): .ttf .ttc .TTF .TTC .dfont
type42 fonts (type42): .t42 .T42
web2c files (web2c):
other text files (othertext):
other binary files (otherbin):
misc fonts (miscfont):
web: .web  .ch
cweb: .w .web  .ch
enc files (enc): .enc
cmap files (cmap):
subfont definition files (sfd): .sfd
opentype fonts (opentype, otf): .otf .OTF
pdftex config (pdftexconfig):
lig files (lig): .lig
texmfscripts:
lua: .lua .luatex .luc .luctex .texlua .texluc .tlu
font feature files (fea): .fea
cid maps (cidmap): .cid .cidmap
mlbib: .mlbib .bib
mlbst: .mlbst .bst
clua: .dll .so
ris: .ris
bltxml: .bltxml
@end example

This option and @samp{--path} are mutually exclusive.

@item --interactive
@opindex --interactive
@cindex interactive query
After processing the command line, read additional filenames to look up
from standard input.

@item --mktex=@var{filetype}
@itemx --no-mktex=@var{filetype}
@opindex --mktex=@var{filetype}
@opindex --no-mktex=@var{filetype}
Turn on or off the @samp{mktex} script associated with @var{filetype}.
Usual values for @var{filetype} are @samp{pk}, @samp{mf}, @samp{tex},
and @samp{tfm}.  By default, all are off in Kpsewhich, even if they
are enabled for @TeX{}.  This option implies setting
@code{--must-exist}.  @xref{mktex scripts}.

@item --mode=@var{string}
@opindex --mode=@var{string}
Set the mode name to @var{string}; this also only affects @samp{gf} and
@samp{pk} lookups.  No default: any mode will be found.  @xref{mktex
script arguments}.

@item --must-exist
@opindex --must-exist
Do everything possible to find the files, notably including searching
the disk and running the @samp{mktex} scripts.  By default, only the
@file{ls-R} database is checked, in the interest of efficiency.

@item --path=@var{string}
@opindex --path=@var{string}
Search along the path @var{string} (colon-separated as usual), instead
of guessing the search path from the filename.  @samp{//} and all the
usual expansions are supported (@pxref{Path expansion}).  This option
and @samp{--format} are mutually exclusive.  To output the complete
directory expansion of a path, instead of doing a one-shot lookup, see
@samp{--expand-path} and @samp{--show-path} in the following section.

@item --progname=@var{name}
@opindex --progname=@var{name}
Set the program name to @var{name}; default is @samp{kpsewhich}.  This
can affect the search paths via the @samp{.@var{prognam}} feature in
configuration files (@pxref{Config files}).

@item --subdir=@var{string}
@opindex --subdir=@var{string}
Report only those matches whose directory part @emph{ends} with
@var{string} (compared literally, except case is ignored on a
case-insensitive operating system).  For example, suppose there are
two matches for a given name:

@example
kpsewhich foo.sty
@result{} /some/where/foo.sty
/another/place/foo.sty
@end example

@noindent
Then we can narrow the result to what we are interested in with
@option{--subdir}:

@example
kpsewhich --subdir=where foo.sty
@result{} /some/where/foo.sty

kpsewhich --subdir=place foo.sty
@result{} /another/place/foo.sty
@end example

@noindent
The string to match must be at the end of the directory part of the
match, and it is taken literally, with no pattern matching:

@example
kpsewhich --subdir=another foo.sty
@result{}
@end example

@noindent
The string to match may cross directory components:

@example
kpsewhich --subdir=some/where foo.sty
@result{} /some/where/foo.sty
@end example

@noindent
@option{--subdir} implies @option{--all}; if there is more than one
match, they will all be reported (in our example, both @samp{where}
and @samp{place} end in @samp{e}):

@example
kpsewhich --subdir=e
@result{} /some/where/foo.sty
/another/place/foo.sty
@end example

@noindent
Because of the above rules, the presence of a leading @samp{/} is
important, since it ``anchors'' the match to a full component name:

@example
kpsewhich --subdir=/lace foo.sty
@result{}
@end example

@noindent
However, a trailing @samp{/} is immaterial (and ignored), since the
match always takes place at the end of the directory part:

@example
kpsewhich --subdir=lace/ foo.sty
@result{} /another/place/foo.sty
@end example

@noindent
The purpose of these rules is to make it convenient to find results
only within a particular area of the tree.  For instance, a given
script named @file{foo.lua} might exist within both
@file{texmf-dist/scripts/pkg1/} and @file{texmf-dist/scripts/pkg2/}.
By specifying, say, @samp{--subdir=/pkg1}, you can be sure of getting
the one you are interested in.

We only match at the end because a site might happen to install @TeX{}
in @file{/some/coincidental/pkg1/path/}, and we wouldn't want to match
@file{texmf-dist/scripts/pkg2/} that when searching for @samp{/pkg1}.

@end table


@node Specially-recognized files
@subsection Specially-recognized files for @command{kpsewhich}

@command{kpsewhich} recognizes a few special filenames on the command
line and defaults to using the `known' file formats for them, merely
to save the time and trouble of specifying the format.  This is only a
feature of @command{kpsewhich}; when using the Kpathsea library
itself, none of these special filenames are recognized, and it's still
up to the caller to specify the desired format.

Here is the list of special filenames to @command{kpsewhich}, along
with their corresponding format:

@table @file

@flindex config.ps
@item config.ps
@code{dvips config}

@flindex dvipdfmx.cfg
@item dvipdfmx.cfg
@samp{other text files}

@flindex fmtutil.cnf
@item fmtutil.cnf
@samp{web2c files}

@flindex glyphlist.txt
@item glyphlist.txt
@samp{map}

@flindex mktex.cnf
@item mktex.cnf
@samp{web2c files}

@flindex pdfglyphlist.txt
@item pdfglyphlist.txt
@samp{map}

@flindex pdftex.cfg
@flindex pdftexconfig.tex
@item pdftex.cfg
@samp{pdftex config} (although @file{pdftex.cfg} is not used any more;
look for the file @file{pdftexconfig.tex} instead.)

@flindex texmf.cnf
@item texmf.cnf
@samp{cnf}

@flindex XDvi
@item XDvi
@samp{other text files}

@end table

A user-specified format will override the above defaults.

@flindex tcfmgr.map
Another reference for information about @TeX{}'s many special files is
@file{tcfmgr.map}, found in @file{texmf/texconfig/tcfmgr.map}, which
records various information about the above configuration files (among
others).


@node Auxiliary tasks
@subsection Auxiliary tasks

@cindex auxiliary tasks

Kpsewhich provides some features in addition to path lookup as such:

@table @samp
@item --debug=@var{num}
@opindex --debug=@var{num}
Set debugging options to @var{num}.  @xref{Debugging}.

@item --expand-braces=@var{string}
@opindex --expand-braces=@var{string}
Output variable, tilde, and brace expansion of @var{string}, which is
assumed to be a single path element.  @xref{Path expansion}.

@item --expand-path=@var{string}
@opindex --expand-path=@var{string}
Output the complete expansion of @var{string}, with each element
separated by the usual path separator on the current system (@samp{;}
on Windows, @samp{:} otherwise).  This may be useful to construct a
custom search path for a format not otherwise supported.  To retrieve
the search path for a format that is already supported, see
@samp{--show-path}.

Nonexistent directories are culled from the output:

@example
$ kpsewhich --expand-path '/tmp'
@result{} /tmp
$ kpsewhich --expand-path '/nonesuch'
@result{}
@end example

For one-shot uses of an arbitrary (not built in to Kpathsea) path, see
@samp{--path} (@pxref{Path searching options}).

@item --expand-var=@var{string}
@opindex --expand-var=@var{string}
Output the variable and tilde expansion of @var{string}.  For example,
with the usual @file{texmf.cnf}, @samp{kpsewhich
--expand-var='$TEXMF'} returns the @TeX{} system hierarchy root(s).
@xref{Path expansion}.  The specified @var{string} can contain
anything, though, not just variable references.  This calls
@code{kpse_var_expand} (@pxref{Programming with config files}).

@item --help-formats
@opindex --help-formats
Output information about each supported format (@pxref{Supported file
formats}), including the names and abbreviations, variables
looked for, and the original path.

@item --safe-extended-in-name=@var{name}
@itemx --safe-extended-out-name=@var{name}
@opindex --safe-extended-in-name=@var{name}
@opindex --safe-extended-out-name=@var{name}
As with @samp{--safe-in-name} and @samp{--safe-out-name} (next item),
but also allow files under the variables @code{TEXMFVAR} and
@code{TEXMFSYSVAR} (@pxref{Calling sequence}).

@item --safe-in-name=@var{name}
@itemx --safe-out-name=@var{name}
@opindex --safe-in-name=@var{name}
@opindex --safe-out-name=@var{name}
Exit successfully if @var{name} is safe to open for reading or
writing, respectively, else unsuccessfully.  No errors are output.
These tests take account of the related Kpathsea configuration
settings (@pxref{Calling sequence}).

@item --show-path=@var{name}
@opindex --show-path=@var{name}
Show the path that would be used for file lookups of file type
@var{name}.  Either a filename extension (@samp{pk}, @samp{.vf}, etc.)
or an integer can be used, just as with @samp{--format}, described in
the previous section.

@item --var-brace-value=@var{variable}
@opindex --var-brace-value=@var{variable}
Like @samp{--var-value} (next), but also expands @samp{@{...@}}
constructs.  (@pxref{Brace expansion}).  Thus, the value is assumed to
possibly be several path elements, and @samp{~} is expanded at the
beginning of each.  The path separator is changed to that of the
current system in the expansion.

Example: @samp{FOO='.;~' kpsewhich --var-brace-value=FOO} outputs (on
a Unix-ish system) @samp{.:/home/karl}, supposing the latter is the
current user's home directory.  Note that the @samp{;} in the source
value, as commonly used in @file{texmf.cnf}, has changed to a
@samp{:}, as the normal path separator on the current system.  On a
Windows-ish system, the @samp{;} would remain.

@item --var-value=@var{variable}
@opindex --var-value=@var{variable}
Outputs the value of @var{variable} (a simple identifier like
@samp{TEXMFDIST}, with no @samp{$} or other constructs), expanding
@samp{$} (@pxref{Variable expansion}) and @samp{~} (@pxref{Tilde
expansion}) constructs in the value.  @samp{~} expansion happens at the
beginning of the overall value and at the beginning of a variable
expansion, but not arbitrarily within the string.  Braces are not expanded.

Example: @samp{--var-value=texmf_casefold_search} outputs (if the
default is not changed) @samp{1}.

Example to contrast with @samp{--var-brace-value}: @samp{FOO='.;~'
kpsewhich --var-value=FOO} outputs @samp{.;~}, i.e., the same as the
input value, on all systems.

@end table


@node Standard options
@subsection Standard options

@cindex standard options

Kpsewhich accepts the standard GNU options:

@itemize @bullet
@item
@opindex --help
@samp{--help} prints a help message on standard output and exits
successfully.

@item
@opindex --version
@samp{--version} prints the Kpathsea version number and exits successfully.
@end itemize


@node TeX support
@chapter @TeX{} support

@cindex @TeX{} support

Although the basic features in Kpathsea can be used for any type of
path searching, it came about, as usual, with a specific application
in mind: I wrote Kpathsea specifically for @TeX{} system programs.  I
had been struggling with the programs I was using (Dvips, Xdvi, and
@TeX{} itself) having slightly different notions of how to specify
paths; and debugging was painful, since no code was shared.

Therefore, Kpathsea provides some @TeX{}-specific formats and
features.  Indeed, many of the purportedly generic path searching
features were provided because they seemed useful in that con@TeX{}t
(font lookup, particularly).

Kpathsea provides a standard way to search for files of any of the
supported file types; glyph fonts are a bit different than all the
rest.  Searches are based solely on names of files, not their
contents---if a GF file is (mis)named @file{cmr10.600pk}, it will be
found as a PK file.

@menu
* Supported file formats::      File types Kpathsea knows about.
* File lookup::                 Searching for most kinds of files.
* Glyph lookup::                Searching for bitmap fonts.
* Suppressing warnings::        Avoiding warnings via TEX_HUSH.
* mktex scripts::               Generating files at runtime.
@end menu


@node Supported file formats
@section Supported file formats

@cindex supported file formats
@cindex file formats, supported

@cindex environment variables for @TeX{}
@cindex @TeX{} environment variables

Kpathsea has support for a number of file types.  Each file type has a
list of environment and config file variables that are checked to define
the search path, and most have a default suffix that plays a role in
finding files (see the next section).  Some also define additional
suffixes, and/or a program to be run to create missing files on the fly.

@cindex program-varying paths
Since environment variables containing periods, such as
@samp{TEXINPUTS.latex}, are not allowed on some systems, Kpathsea looks
for environment variables with an underscore, e.g.,
@samp{TEXINPUTS_latex} (@pxref{Config files}).

The following table lists the above information.  You can also get the
list by giving the @samp{--help-formats} option to @code{kpsewhich}
(@pxref{Auxiliary tasks}).

@table @samp
@item afm
@flindex .afm
@vindex AFMFONTS
(Adobe font metrics, @pxref{Metric files,,, dvips, Dvips})
@code{AFMFONTS};
suffix @samp{.afm}.

@item base
@flindex .base
@vindex MFBASES
@vindex TEXMFINI
(Metafont memory dump, @pxref{Memory dumps,,, web2c, Web2c})
@code{MFBASES}, @code{TEXMFINI};
suffix @samp{.base}.

@item bib
@flindex .bib
@vindex BIBINPUTS
@vindex TEXBIB
(Bib@TeX{} bibliography source, @pxref{bibtex invocation,,, web2c, Web2c})
@code{BIBINPUTS}, @code{TEXBIB};
suffix @samp{.bib}.

@item bltxml
@flindex .bltxml
@vindex BLTXMLINPUTS
(Bib@LaTeX{}ML bibliography files for Biber, @url{https://ctan.org/pkg/biber})
@code{BLTXMLINPUTS}
suffix @samp{.bltxml}.

@item bst
@flindex .bst
@vindex BSTINPUTS
(Bib@TeX{} style, @pxref{Basic BibTeX style files,, Basic Bib@TeX{}
style files, web2c, Web2c})
@code{BSTINPUTS};
suffix @samp{.bst}.

@item clua
@flindex .dll
@flindex .so
@vindex CLUAINPUTS
(dynamic libraries for Lua, @url{https://ctan.org/pkg/luatex})
@code{CLUAINPUTS}
suffixes @samp{.dll} and @samp{.so}.

@item cmap
@flindex .cmap
@vindex CMAPFONTS
(character map files)
@code{CMAPFONTS};
suffix @samp{.cmap}.

@item cnf
@flindex .cnf
@vindex TEXMFCNF
(Runtime configuration files, @pxref{Config files})
@code{TEXMFCNF};
suffix @samp{.cnf}.

@item cweb
@flindex .w
@flindex .web
@vindex CWEBINPUTS
(CWEB input files)
@code{CWEBINPUTS};
suffixes @samp{.w}, @samp{.web};
additional suffix @samp{.ch}.

@item dvips config
@vindex TEXCONFIG
@flindex config.ps@r{, search path for}
(Dvips @samp{config.*} files, such as @file{config.ps}, @pxref{Config
files,,, dvips, Dvips})
@code{TEXCONFIG}.

@item enc files
@flindex .enc
@vindex ENCFONTS
(encoding vectors)
@code{ENCFONTS};
suffix @samp{.enc}.

@item fmt
@flindex .fmt
@vindex TEXFORMATS
@vindex TEXMFINI
(@TeX{} memory dump, @pxref{Memory dumps,,, web2c, Web2c})
@code{TEXFORMATS}, @code{TEXMFINI};
suffix @samp{.fmt}.

@item font cid map
@flindex .cid
@vindex FONTCIDMAPS
(CJK mapping)
@code{FONTCIDMAPS}
suffix @samp{.cid}.

@item font feature files
@flindex .fea
@vindex FONTFEATURES
(primarily for OpenType font features)
@code{FONTFEATURES}
suffix @samp{.fea}.

@item gf
@flindex gf
@vindex GFFONTS
@vindex GLYPHFONTS
@vindex TEXFONTS
(generic font bitmap, @pxref{Glyph files,,, dvips, Dvips})
@code{@var{program}FONTS}, @code{GFFONTS}, @code{GLYPHFONTS}, @code{TEXFONTS};
suffix @samp{gf}.

@item graphic/figure
@flindex .eps
@flindex .epsi
@vindex TEXPICTS
@vindex TEXINPUTS
(Encapsulated PostScript figures, @pxref{PostScript figures,,, dvips, Dvips})
@code{TEXPICTS}, @code{TEXINPUTS};
additional suffixes: @samp{.eps}, @samp{.epsi}.

@item ist
@flindex .ist
@vindex TEXINDEXSTYLE
@vindex INDEXSTYLE
(makeindex style files)
@code{TEXINDEXSTYLE}, @code{INDEXSTYLE};
suffix @samp{.ist}.

@item lig files
@flindex .lig
@vindex LIGFONTS
(ligature definition files)
@code{LIGFONTS};
suffix @samp{.lig}.

@item ls-R
@flindex ls-R
@vindex TEXMFDBS
(Filename databases, @pxref{Filename database})
@code{TEXMFDBS}.

@item lua
@flindex .lua
@flindex .luatex
@flindex .luc
@flindex .luctex
@flindex .texlua
@flindex .texluc
@flindex .tlu 
@vindex LUAINPUTS
(Lua scripts, @url{https://ctan.org/pkg/luatex})
@code{LUAINPUTS}
suffixes @samp{.lua}, @samp{.luatex}, @samp{.luc}, @samp{.luctex},
@samp{.texlua}, @samp{.texluc}, @samp{.tlu}.

@item map
@flindex .map
@vindex TEXFONTMAPS
(Fontmaps, @pxref{Fontmap})
@code{TEXFONTMAPS};
suffix @samp{.map}.

@item mem
@flindex .mem
@vindex MPMEMS
@vindex TEXMFINI
(MetaPost memory dump, @pxref{Memory dumps,,, web2c, Web2c})
@code{MPMEMS}, @code{TEXMFINI};
suffix @samp{.mem}.

@item @r{MetaPost support}
@vindex MPSUPPORT
(MetaPost support files, used by DMP; @pxref{dmp invocation,,, web2c, Web2c})
@code{MPSUPPORT}.

@item mf
@flindex .mf
@vindex MFINPUTS
(Metafont source, @pxref{mf invocation,,, web2c, Web2c})
@code{MFINPUTS};
suffix @samp{.mf};
dynamic creation program: @code{mktexmf}.

@item mfpool
@flindex .pool
@vindex MFPOOL
(Metafont program strings, @pxref{pooltype invocation,,, web2c, Web2c})
@code{MFPOOL}, @code{TEXMFINI};
suffix @samp{.pool}.

@item mft
@flindex .mft
@vindex MFTINPUTS
(@code{MFT} style file, @pxref{mft invocation,,, web2c, Web2c})
@code{MFTINPUTS};
suffix @samp{.mft}.

@item misc fonts
@vindex MISCFONTS
(font-related files that don't fit the other categories)
@code{MISCFONTS}

@item mlbib
@flindex .mlbib
@vindex MLBIBINPUTS
@vindex BIBINPUTS
@vindex TEXBIB
(MlBib@TeX{} bibliography source)
@code{MLBIBINPUTS}, @code{BIBINPUTS}, @code{TEXBIB};
suffixes @samp{.mlbib}, @samp{.mlbib}.

@item mlbst
@flindex .mlbst
@vindex MLBSTINPUTS
@vindex BSTINPUTS
(MlBib@TeX{} style)
@code{MLBSTINPUTS}, @code{BSTINPUTS};
suffixes @samp{.mlbst}, @samp{.bst}.

@item mp
@flindex .mp
@vindex MPINPUTS
(MetaPost source, @pxref{mpost invocation,,, web2c, Web2c})
@code{MPINPUTS};
suffix @samp{.mp}.

@item mppool
@flindex .pool
@vindex MPPOOL
(MetaPost program strings, @pxref{pooltype invocation,,, web2c, Web2c})
@code{MPPOOL}, @code{TEXMFINI};
suffix @samp{.pool}.

@item ocp
@flindex .ocp
@vindex OCPINPUTS
(Omega compiled process files)
@code{OCPINPUTS}; @*
suffix @samp{.ocp};
dynamic creation program: @code{MakeOmegaOCP}.

@item ofm
@flindex .ofm
@vindex OFMFONTS
(Omega font metrics)
@code{OFMFONTS}, @code{TEXFONTS}; @*
suffixes @samp{.ofm}, @samp{.tfm};
dynamic creation program: @code{MakeOmegaOFM}.

@item opentype fonts
@vindex OPENTYPEFONTS
(OpenType fonts)
@code{OPENTYPEFONTS}.

@item opl
@flindex .opl
(Omega property lists)
@code{OPLFONTS}, @code{TEXFONTS};
suffix @samp{.opl}.

@item otp
@flindex .otp
@vindex OTPINPUTS
(Omega translation process files)
@code{OTPINPUTS};
suffix @samp{.otp}.

@item ovf
@flindex .ovf
@vindex OVFFONTS
(Omega virtual fonts)
@code{OVFFONTS}, @code{TEXFONTS};
suffix @samp{.ovf}.

@item ovp
@flindex .ovp
@vindex OVPFONTS
(Omega virtual property lists)
@code{OVPFONTS}, @code{TEXFONTS};
suffix @samp{.ovp}.

@item pdftex config
@vindex PDFTEXCONFIG
(PDF@TeX{}-specific configuration files)
@code{PDFTEXCONFIG}.

@item pk
@flindex .pk
@vindex PKFONTS
@vindex TEXPKS
@vindex GLYPHFONTS
@vindex TEXFONTS
(packed bitmap fonts, @pxref{Glyph files,,, dvips, Dvips})
@code{@var{PROGRAM}FONTS} (@var{program} being @samp{XDVI}, etc.),
@code{PKFONTS}, @code{TEXPKS}, @code{GLYPHFONTS}, @code{TEXFONTS};
suffix @samp{pk};
dynamic creation program: @code{mktexpk}.

@item PostScript header
@flindex .pro
@vindex TEXPSHEADERS
@vindex PSHEADERS
(downloadable PostScript, @pxref{Header files,,, dvips, Dvips})
@code{TEXPSHEADERS}, @code{PSHEADERS};
additional suffix @samp{.pro}.

@item ris
@flindex .ris
@vindex RISINPUTS
(RIS bibliography files, primarily for Biber, @url{https://ctan.org/pkg/biber})
@code{RISINPUTS}
suffix @samp{.ris}.

@item subfont definition files
@flindex .sfd
@vindex SFDFONTS
(subfont definition files)
@code{SFDFONTS}
suffix @samp{.sfd}.

@item tex
@flindex .tex
@vindex TEXINPUTS
(@TeX{} source, @pxref{tex invocation,,, web2c, Web2c})
@code{TEXINPUTS};
suffix @samp{.tex};
additional suffixes: none, because such a list cannot be complete;
dynamic creation program: @code{mktextex}.

@item TeX system documentation
@flindex doc files
@vindex TEXDOCS
(Documentation files for the @TeX{} system)
@code{TEXDOCS}.

@item TeX system sources
@flindex source files
@vindex TEXSOURCES
(Source files for the @TeX{} system)
@code{TEXSOURCES}.

@item texmfscripts
@vindex TEXMFSCRIPTS
(Architecture-independent executables distributed in the texmf trees)
@code{TEXMFSCRIPTS}.

@item texpool
@flindex .pool
@vindex TEXPOOL
(@TeX{} program strings, @pxref{pooltype invocation,,, web2c, Web2c})
@code{TEXPOOL}, @code{TEXMFINI};
suffix @samp{.pool}.

@item tfm
@flindex .tfm
@vindex TFMFONTS
@vindex TEXFONTS
(@TeX{} font metrics, @pxref{Metric files,,, dvips, Dvips})
@code{TFMFONTS}, @code{TEXFONTS};
suffix @samp{.tfm};
dynamic creation program: @code{mktextfm}.

@item Troff fonts
@vindex TRFONTS
(Troff fonts, used by DMP; @pxref{DMP invocation,,, web2c, Web2c})
@code{TRFONTS}.

@item truetype fonts
@flindex .ttf
@flindex .ttc
@vindex TTFONTS
(TrueType outline fonts) @code{TTFONTS}; suffixes @samp{.ttf} and
@samp{.TTF}, @samp{.ttc} and @samp{.TTC}, @samp{.dfont}.

@item type1 fonts
@flindex .pfa
@flindex .pfb
@vindex T1FONTS
@vindex T1INPUTS
@vindex TEXPSHEADERS
@vindex DVIPSHEADERS
(Type 1 PostScript outline fonts, @pxref{Glyph files,,, dvips, Dvips})
@code{T1FONTS}, @code{T1INPUTS}, @code{TEXPSHEADERS}, @code{DVIPSHEADERS};
suffixes @samp{.pfa}, @samp{.pfb}.

@item type42 fonts
@vindex T42FONTS
(Type 42 PostScript outline fonts) @code{T42FONTS}.

@item vf
@flindex .vf
@vindex VFFONTS
@vindex TEXFONTS
(virtual fonts, @pxref{Virtual fonts,,, dvips, Dvips})
@code{VFFONTS}, @code{TEXFONTS};
suffix @samp{.vf}.

@item web
@flindex .web
@vindex WEBINPUTS
(WEB input files)
@code{WEBINPUTS};
suffix @samp{.web};
additional suffix @samp{.ch}.

@item web2c files
@vindex WEB2C
(files specific to the web2c implementation)
@code{WEB2C}.
@end table

There are two special cases, because the paths and environment variables
always depend on the name of the program: the variable name is
constructed by converting the program name to upper case, and then
appending @samp{INPUTS}.  Assuming the program is called @samp{foo},
this gives us the following table.

@table @samp
@item other text files
@vindex FOOINPUTS
(text files used by @samp{foo})
@code{FOOINPUTS}.

@item other binary files
@vindex FOOINPUTS
(binary files used by @samp{foo})
@code{FOOINPUTS}.
@end table

If an environment variable by these names are set, the corresponding
@file{texmf.cnf} definition won't be looked at (unless, as usual, the
environment variable value has an extra @samp{:}).  @xref{Default
expansion}.

For the font variables, the intent is that:
@itemize @bullet
@item
@code{TEXFONTS} is the default for everything.

@item
@code{GLYPHFONTS} is the default for bitmap (or, more precisely,
non-metric) files.

@item
Each font format has a variable of its own.

@item
@vindex XDVIFONTS
@vindex DVIPSFONTS
Each program has its own font override path as well; e.g.,
@code{DVIPSFONTS} for Dvipsk.  Again, this is for bitmaps, not metrics.

@end itemize


@node File lookup
@section File lookup

@cindex file lookup
@cindex searching for files
@cindex @TeX{} file lookup

This section describes how Kpathsea searches for most files (bitmap font
searches are the exception, as described in the next section).

Here is the search strategy for a file @var{name}:

@enumerate
@item
If the file format defines default suffixes, and the suffix of
@var{name} name is not already a known suffix for that format, try the
name with each default appended, and use alternative names found in
the fontmaps if necessary.  Example: given @samp{foo.bar}, look for
@samp{foo.bar.tex}.

@item
Search for @var{name}, and if necessary for alternative names found in
the fontmaps.  Example: given @samp{foo.bar}, we also look for
@samp{foo.bar}.

@item
If the file format defines a program to invoke to create missing files,
run it (@pxref{mktex scripts}).
@end enumerate

@cindex extensions, filename
@cindex suffixes, filename
@vindex try_std_extension_first
The order in which we search for ``suffixed'' name (item@tie{}1) or
the ``as-is'' name (item@tie{}2) is controlled by the
@file{try_std_extension_first} configuration value.  The default set
in @file{texmf.cnf} is true, since common suffixes are already
recognized: @samp{babel.sty} will only look for @samp{babel.sty}, not
@samp{babel.sty.tex}, regardless of this setting.

When the suffix is unknown (e.g., @samp{foo.bar}), both names are
always tried; the difference is the order in which they are tried.

@file{try_std_extension_first} only affects names being looked up
which *already* have an extension.  A name without an extension (e.g.,
@samp{tex story}) will always have an extension added first.

@flindex tex-file.c
@findex kpathsea_find_file
This algorithm is implemented in the function
@code{kpathsea_find_file} in the source file
@file{kpathsea/tex-file.c}.  You can watch it in action with the
debugging options (@pxref{Debugging}).


@node Glyph lookup
@section Glyph lookup

@cindex glyph lookup
@cindex searching for glyphs
@cindex @TeX{} glyph lookup

This section describes how Kpathsea searches for a bitmap font in GF or
PK format (or either) given a font name (e.g., @samp{cmr10}) and a
resolution (e.g., 600).

Here is an outline of the search strategy (details in the sections
below) for a file @var{name} at resolution @var{dpi}.  The search stops
at the first successful lookup.

@enumerate
@item
Look for an existing file @var{name}.@var{dpi}@var{format} in the
specified format(s).

@item If @var{name} is an alias for a file @var{f} in the fontmap
file @file{texfonts.map}, look for @var{f}.@var{dpi}.

@item Run an external program (typically named @samp{mktexpk}) to
generate the font (@pxref{mktex scripts})

@item Look for @var{fallback}.@var{dpi}, where @var{fallback} is some
last-resort font (typically @samp{cmr10}).
@end enumerate

@flindex tex-glyph.c
@findex kpathsea_find_glyph
This is implemented in @code{kpathsea_find_glyph} in
@file{kpathsea/tex-glyph.c}.

@menu
* Basic glyph lookup::          Features common to all glyph lookups.
* Fontmap::                     Aliases for fonts.
* Fallback font::               Resolutions and fonts of last resort.
@end menu


@node Basic glyph lookup
@subsection Basic glyph lookup

@cindex basic glyph lookup
@cindex common features in glyph lookup

When Kpathsea looks for a bitmap font @var{name} at resolution @var{dpi}
in a format @var{format}, it first checks each directory in the search
path for a file @samp{@var{name}.@var{dpi}@var{format}}; for example,
@samp{cmr10.600pk}.  Kpathsea looks for a PK file first, then a GF file.

If that fails, Kpathsea looks for
@samp{dpi@var{dpi}/@var{name}.@var{format}}; for example,
@samp{dpi600/cmr10.pk}. This is how fonts are typically stored on
filesystems (such as DOS) that permit only three-character extensions.

@cindex tolerance for glyph lookup
@cindex glyph lookup bitmap tolerance
@findex KPSE_BITMAP_TOLERANCE
If that fails, Kpathsea looks for a font with a close-enough @var{dpi}.
``Close enough'' is defined by the macro @code{KPSE_BITMAP_TOLERANCE} in
@file{kpathsea/tex-glyph.h} to be @code{@var{dpi} / 500 + 1}.  This is
slightly more than the 0.2% minimum allowed by the DVI standard
(@url{@var{CTAN:}/dviware/driv-standard/level-0}).


@node Fontmap
@subsection Fontmap

@cindex fontmap files
@cindex font alias files
@cindex aliases for fonts

@flindex texfonts.map
If a bitmap font or metric file is not found with the original name (see
the previous section), Kpathsea looks through any @dfn{fontmap} files
for an @dfn{alias} for the original font name.  These files are named
@file{texfonts.map} and searched for along the @code{TEXFONTMAPS}
environment/config file variable.  All @file{texfonts.map} files that
are found are read; earlier definitions override later ones.

This feature is intended to help in two respects:

@enumerate

@item
@cindex fontnames, arbitrary length
An alias name is limited in length only by available memory, not by your
filesystem.  Therefore, if you want to ask for @samp{Times-Roman}
instead of @file{ptmr}, you can (you get @samp{ptmr8r}).

@item
@cindex circle fonts
@flindex lcircle10
A few fonts have historically had multiple names: specifically,
La@TeX{}'s ``circle font'' has variously been known as @file{circle10},
@file{lcircle10}, and @file{lcirc10}.  Aliases can make all the names
equivalent, so that it no longer matters what the name of the installed
file is; @TeX{} documents will find their favorite name.

@end enumerate

The format of fontmap files:

@itemize @bullet
@cindex comments, in fontmap files
@item Comments start with the last @samp{%} on a line and continue to
the end of the line. (This provides for names that include a %,
ill-advised as that may be.)

@cindex whitespace, in fontmap files
@item Blank lines are ignored.

@item Each nonblank line is broken up into a series of @dfn{words}:
  a sequence of non-whitespace characters.

@findex include @r{fontmap directive}
@item If the first word is @samp{include}, the second word is used as
  a filename, and it is searched for and read.

@item Otherwise, the first word on each line is the true filename;

@item the second word is the alias;

@item subsequent words are ignored.
@end itemize

If an alias has an extension, it matches only those files with that
extension; otherwise, it matches anything with the same root, regardless
of extension.  For example, an alias @samp{foo.tfm} matches only when
@file{foo.tfm} is being searched for; but an alias @samp{foo} matches
@file{foo.vf}, @file{foo.600pk}, etc.

As an example, here is an excerpt from the @file{texfonts.map} in the
Web2c distribution.  It makes the old and new names of the @LaTeX{}
circle fonts equivalent.

@example
circle10        lcircle10
circle10        lcirc10
lcircle10       circle10
lcircle10       lcirc10
lcirc10         circle10
lcirc10         lcircle10
@dots{}
@end example

Fontmaps are implemented in the file @file{kpathsea/fontmap.c}.
The Fontname distribution has much more information on font naming
(@pxref{,,,fontname, Filenames for @TeX{} fonts}).


@node Fallback font
@subsection Fallback font

@cindex fallback font
@cindex fallback resolutions
@cindex font of last resort
@cindex resolutions, last-resort
@cindex last-resort font

@vindex DVIPSSIZES
@vindex XDVISIZES
@vindex DVILJSIZES
@vindex TEXSIZES
@vindex default_texsizes
If a bitmap font cannot be found or created at the requested size,
Kpathsea looks for the font at a set of @dfn{fallback resolutions}.  You
specify these resolutions as a colon-separated list (like search paths).
Kpathsea looks first for a program-specific environment variable (e.g.,
@code{DVIPSSIZES} for Dvipsk), then the environment variable
@code{TEXSIZES}, then a default specified at compilation time (the Make
variable @code{default_texsizes}).  You can set this list to be empty if
you prefer to find fonts at their stated size or not at all.

@flindex cmr10@r{, as fallback font}
@findex kpathsea_init_prog
Finally, if the font cannot be found even at the fallback resolutions,
Kpathsea looks for a fallback font, typically @file{cmr10}.  Programs
must enable this feature by  calling @code{kpathsea_init_prog}
(@pxref{Calling sequence}); the default is no fallback font.


@node Suppressing warnings
@section Suppressing warnings

@cindex warnings, suppressing
@cindex suppressing warnings

@vindex TEX_HUSH
Kpathsea provides a way to suppress selected usually-harmless warnings;
this is useful at large sites where most users are not administrators,
and thus the warnings are merely a source of confusion, not a help.  To
do this, you set the environment variable or configuration file value
@code{TEX_HUSH} to a colon-separated list of values.  Here are the
possibilities:

@vtable @samp
@item all
Suppress everything possible.

@item checksum
@cindex mismatched checksum warnings
Suppress mismatched font checksum warnings.

@item lostchar
@cindex missing character warnings
Suppress warnings when a character is missing from a font that a DVI or
VF file tries to typeset.

@item none
Don't suppress any warnings.

@item readable
@cindex unreadable file warnings
Suppress warnings about attempts to access a file whose permissions
render it unreadable.

@item special
@cindex unknown special warnings
@findex \special@r{, suppressing warnings about}
Suppresses warnings about an unimplemented or unparsable
@samp{\special} command.
@end vtable

@noindent @file{tex-hush.c} defines the function that checks the
variable value.  Each driver implements its own checks where
appropriate.


@node mktex scripts
@section @file{mktex} scripts

@cindex @file{mktex} scripts
@cindex scripts for file creation

@cindex font set, infinite
@cindex dynamic creation of files
@cindex Sauter fonts, and dynamic source creation
@cindex EC fonts, and dynamic source creation
If Kpathsea cannot otherwise find a file, for some file types it is
configured by default to invoke an external program to create it
dynamically (@pxref{mktex configuration}).  These are collectively
known as @dfn{@code{mktex} scripts}, since most of them are named
@code{mktex...}.

For example, this is useful for fonts (bitmaps, TFM's, and
arbitrarily-sizable Metafont sources such as the Sauter and EC fonts),
since any given document can use fonts never before referenced.
Building all fonts in advance is therefore impractical, if not
impossible.

It is also useful for the @TeX{} @samp{.fmt} (and Metafont
@samp{.base} and Metapost @samp{.mem} files, @pxref{Memory
dumps,,,Web2c,web2c}), where pre-generating every format consumes a
lot of both time and space.

The script is passed the name of the file to create and possibly other
arguments, as explained below.  It must echo the full pathname of the
file it created (and nothing else) to standard output; it can write
diagnostics to standard error.

@menu
* config: mktex configuration.
* names: mktex script names.
* args: mktex script arguments.
@end menu


@node mktex configuration
@subsection @file{mktex} configuration

@cindex @file{mktex} script configuration
@cindex configuration of @file{mktex} scripts
@cindex enabling @file{mktex} scripts
@cindex disabling @file{mktex} scripts

The list of file types and program names that can run an external
program to create missing files is listed in the next section.  In the
absence of @code{configure} options specifying otherwise, everything
but @file{mktextex} will be enabled by default.  The @code{configure}
options to change the defaults are:

@cindex @code{configure} options for @file{mktex} scripts
@opindex --without-mktexfmt-default
@opindex --without-mktexmf-default
@opindex --without-mktexocp-default
@opindex --without-mktexofm-default
@opindex --without-mktexpk-default
@opindex --without-mktextfm-default
@opindex --with-mktextex-default
@example
--without-mktexfmt-default
--without-mktexmf-default
--without-mktexocp-default
--without-mktexofm-default
--without-mktexpk-default
--without-mktextfm-default
--with-mktextex-default
@end example

The @code{configure} setting is overridden if the environment variable
or configuration file value named for the script is set; e.g.,
@file{MKTEXPK} (@pxref{mktex script arguments}).

@flindex fmtutils.cnf
@code{mktexfmt} reads a file @file{fmtutil.cnf}, typically located in
@file{texmf/web2c/} to glean its configuration information.  The rest
of the files and features in this section are primarily intended for
the font generation scripts.

@flindex mktex.cnf
@flindex mktex.opt
@cindex site overrides for @code{mktex@dots{}}
As distributed, all the scripts source a file
@file{texmf/web2c/mktex.cnf} if it exists, so you can override various
defaults.  
See @file{mktex.opt}, for instance, which defines the default mode,
resolution, some special directory names, etc.  If you prefer not to
change the distributed scripts, you can simply create @file{mktex.cnf}
with the appropriate definitions (you do not need to create it if you
have nothing to put in it).  @file{mktex.cnf} has no special syntax;
it's an arbitrary Bourne shell script.  The distribution contains a
sample @file{mktex.cnf} for you to copy and modify as you please (it
is not installed anywhere).

@flindex mktex.opt
@vindex MT_FEATURES
In addition, you can configure a number of features with the
@code{MT_FEATURES} variable, which you can define:

@itemize @bullet
@item
in @file{mktex.opt}, as just mentioned;

@item
by editing the file @file{mktex.opt}, either before @samp{make
install} (in the source hierarchy) or after (in the installed
hierarchy);

@item
or in the environment.
@end itemize

If none of the options below are enabled, @code{mktexpk},
@code{mktextfm}, and @code{mktexmf} follow the following procedure to
decide where fonts should be installed.  Find the tree where the font's
sources are, and test the permissions of the @samp{fonts} directory of
that tree to determine whether it is writable.  If it is, put the files
in the tree in appropriate locations.  If it isn't writable, see whether
the tree is a system tree (named in @code{SYSTEXMF}).  If so, the
@code{VARTEXFONTS} tree is used.  In all other cases the working
directory is used.

The @samp{appendonlydir} option is enabled by default.

@vtable @samp
@item appendonlydir
@cindex directories, making append-only
@flindex mktexdir
Tell @code{mktexdir} to create directories append-only, i.e., set
their sticky bit (@pxref{Mode Structure,,, coreutils, GNU Core
Utilities}).  This feature is silently ignored on non-Unix platforms
(e.g. Windows/NT and MS-DOS) which don't support similar functionality.
This feature is enabled by default.

@item dosnames
@cindex 8.3 filenames, using
@cindex DOS compatible names
@flindex dpi@var{nnn} directories
Use 8.3 names; e.g., @file{dpi600/cmr10.pk} instead of
@file{cmr10.600pk}.  Note that this feature only affects filenames that
would otherwise clash with other TeX-related filenames; @file{mktex}
scripts do nothing about filenames which exceed the 8+3 MS-DOS limits
but remain unique when truncated (by the OS) to these limits, and nether
do the scripts care about possible clashes with files which aren't
related with TeX.  For example, @file{cmr10.600pk} would clash with
@file{cmr10.600gf} and is therefore changed when @samp{dosnames} is in
effect, but @file{mf.pool} and @file{mp.base} don't clash with any
TeX-related files and are therefore unchanged.

This feature is turned on by default on MS-DOS.  If you do not wish
@samp{dosnames} to be set on an MS-DOS platform, you need to set the
@code{MT_FEATURES} environment variable to a value that doesn't include
@samp{dosnames}.  You can also change the default setting by editing
@file{mktex.opt}, but only if you use the @file{mktex} shell scripts;
the emulation programs don't consult @file{mktex.opt}.

@item fontmaps
@cindex fontmaps
@cindex fontname
Instead of deriving the location of a font in the destination tree from
the location of the sources, the aliases and directory names from the
Fontname distribution are used. (@pxref{Top,, Introduction, fontname,
Fontname}).

@item nomfdrivers
@cindex metafont driver files
Let mktexpk and mktextfm create metafont driver files in a temporary
directory.  These will be used for just one metafont run and not
installed permanently.

@item nomode
@cindex mode directory, omitting
Omit the directory level for the mode name; this is fine as long as
you generate fonts for only one mode.

@item stripsupplier
@cindex supplier directory, omitting
Omit the font supplier name directory level.

@item striptypeface
@cindex typeface directory, omitting
Omit the font typeface name directory level.

@item strip
@cindex supplier directory, omitting
@cindex typeface directory, omitting
Omit the font supplier and typeface name directory levels.  This feature
is deprecated in favour of @samp{stripsupplier} and @samp{striptypeface}.

@item varfonts
@flindex /var/tmp/texfonts
@vindex VARTEXFONTS
@cindex Linux File System Standard
When this option is enabled, fonts that would otherwise be written in
system texmf tree go to the @code{VARTEXFONTS} tree instead.  The
default value in @file{kpathsea/Makefile.in} is
@file{/var/tmp/texfonts}.  The @cite{Linux File System Standard}
recommends @file{/var/tex/fonts}.

@vindex USE_VARTEXFONTS
The @samp{varfonts} setting in @code{MT_FEATURES} is overridden by the
@code{USE_VARTEXFONTS} environment variable: if set to @samp{1}, the
feature is enabled, and if set to @samp{0}, the feature is disabled.

@item texmfvar
@vindex TEXMFVAR
Force generated files that would go into a system tree (as defined by
@code{SYSTEXMF}) into @code{TEXMFVAR}. Starting with te@TeX{}-3.0, the
variable @code{TEXMFVAR} is always set.  The @samp{varfonts} feature takes
precedence if also set.

@vindex USE_TEXMFVAR
The @samp{texmfvar} setting in @code{MT_FEATURES} is overridden by the
@code{USE_TEXMFVAR} environment variable: if set to @samp{1}, the
feature is enabled, and if set to @samp{0}, the feature is disabled.
@end vtable


@node mktex script names
@subsection @file{mktex} script names

@cindex @file{mktex} script names
@cindex names for @file{mktex} scripts

The following table shows the default name of the script for each
of the file types which support runtime generation.

@table @file
@item mktexfmt
@pindex mktexfmt
@pindex fmtutil
(@samp{.fmt}, @samp{.base}, @samp{.mem}) @TeX{}/Metafont/MetaPost
formats.  This script is also named @command{fmtutil}, and reads
@file{fmtutil.cnf} for configuration information.

@item mktexmf
@pindex mktexmf
(@samp{.mf}) Metafont input files.

@item mkocp
@pindex mkocp
(@samp{.ocp}) Omega compiled process files.

@item mkofm
@pindex mkofm
(@samp{.ofm}) Omega font metric files.

@item mktexpk
@pindex mktexpk
(@samp{pk}) Glyph fonts.

@item mktextex
@pindex mktextex
(@samp{.tex}) @TeX{} input files (disabled by default).

@item mktextfm
@pindex mktextfm
(@samp{.tfm}) TFM files.
@end table

@vindex DVIPSMAKEPK
@vindex XDVIMAKEPK
@vindex DVILJMAKEPK
@noindent These names can be overridden by an environment variable specific
to the program; for example, @code{DVIPSMAKEPK} for Dvipsk.

@comment next two paragraphs are repeated in dvips.texi
@flindex missfont.log
@cindex failed @code{mktex@dots{}} script invocation
If a @code{mktex@dots{}} script fails, the invocation is appended to a
file @file{missfont.log} (by default) in the current directory.  After
fixing the problem, you can then execute the log file to create the
missing files.

@vindex TEXMF_OUTPUT_DIRECTORY@r{, and @file{missfont.log}}
@vindex TEXMFOUTPUT@r{, and @file{missfont.log}}
If the environment variable @code{TEXMF_OUTPUT_DIRECTORY} is set,
@file{missfont.log} is first tried to be written there; if it's not
set, the current directory is tried first.  If that first write fails
and the environment variable or configuration file value
@code{TEXMFOUTPUT} is set, we try to write @file{missfont.log} there.
Otherwise nothing is written.

@vindex MISSFONT_LOG
The base filename @samp{missfont.log} is overridden by the
@code{MISSFONT_LOG} environment variable or configuration file value.


@node mktex script arguments
@subsection @file{mktex} script arguments

@cindex arguments to @file{mktex}

The first argument to a @file{mktex} script is always the name
of the file to be created.

In the default @file{mktexpk} implementation, additional arguments may
also be passed:

@table @samp
@item --dpi @var{num}
Sets the resolution of the generated font to @var{num}.
@item --mfmode @var{name}
Sets the Metafont mode to @var{name}.
@item --bdpi @var{num}
Sets the ``base dpi'' for the font.  This must match the mode being
used.
@item --mag @var{string}
A ``magstep'' string suitable for the Metafont @code{mag} variable.
This must match the combination of @var{bdpi} and @var{dpi} being used.
@item --destdir @var{string}
A directory name. If the directory is absolute, it is used as-is.
Otherwise, it is appended to the root destination directory set in the
script.
@end table


@node Programming
@chapter Programming

This chapter is for programmers who wish to use Kpathsea.
@xref{Introduction}, for the conditions under which you may do so (in
short, it is released under LGPLv2.1 or later).

@menu
* Overview: Programming overview.         Introduction.
* Calling sequence::                      Specifics of what to call.
* Safe filenames::                        Only opening allowed files.
* Program-specific files::                How to handle these.
* Config: Programming with config files.  Getting info from texmf.cnf.
@end menu


@node Programming overview
@section Programming overview

@cindex programming overview
@cindex overview of programming with Kpathsea

Aside from this manual, your best source of information is the source
to the programs that use Kpathsea (@pxref{Introduction}).  First,
Kpsewhich is a small utility program whose sole purpose is to exercise
the main path-searching functionality.  Of the drivers, Dviljk is
probably the simplest full application program.  Xdvik adds VF support
and the complication of X resources.  Dvipsk adds the complication of
its own config files.  Web2c is source code I also maintain, so it
uses Kpathsea rather straightforwardly, but is of course complicated
by the Web to C translation.

@cindex re-entrant API
@cindex API, re-entrant
When looking at these program sources, you should know that previous
versions of the library had a different programming interface; the
current interface supports re-entrancy.  Historically, the library
function names were prefixed with @code{kpse_} instead of
@code{kpathsea_}, and they did not need an instance variable as first
argument.  This change was made in 2009.  The old functions will never
disappear, and can reliably continue to be used when they suffice, as
they do for the programs above.  The main application using the
re-entrant API is the MetaPost library used by MetaPost and Lua@TeX{}.

@flindex pathsearch.h
@flindex tex-file.h
@flindex tex-glyph.h
@flindex kpathsea.h
Beyond these examples, the @file{.h} files in the Kpathsea source
describe the interfaces and functionality (and of course the @file{.c}
files define the actual routines, which are the ultimate documentation).
@file{pathsearch.h} declares the basic searching routine.
@file{tex-file.h} and @file{tex-glyph.h} define the interfaces for
looking up particular kinds of files.  In view of the way the headers
depend on each other, it is recommended to use @code{#include
<kpathsea/kpathsea.h>}, which includes every Kpathsea header.

@flindex config.h
@flindex c-auto.h
If you want to include only specific headers, you should still
consider including @file{kpathsea/config.h} before including any other
Kpathsea header, as it provides symbols used in the other headers;
@file{kpathsea/config.h} includes @file{kpathsea/c-auto.h}, which is
generated by Autoconf.

@cindex file types, registering new
The library provides no way for an external program to register new file
types: @file{tex-file.[ch]} must be modified to do this. For example,
Kpathsea has support for looking up Dvips config files, even though no
program other than Dvips is likely to ever want to do so.  I felt this
was acceptable, since along with new file types should also come new
defaults in @file{texmf.cnf} (and its descendant @file{paths.h}), since
it's simplest for users if they can modify one configuration file for
all kinds of paths.

Kpathsea does not parse any formats itself; it barely opens any files.
Its primary purpose is to return filenames.  The GNU font utilities
package contains libraries to read TFM, GF, and PK files, as do the
programs above, of course.


@node Calling sequence
@section Calling sequence

@cindex programming with Kpathsea
@cindex calling sequence

The typical way to use Kpathsea in your program goes something like this:

@enumerate

@item
@findex kpathsea_new
Call @code{kpathsea_new} to create a new library instance. This variable
must be passed as the first argument to all the following library functions.
The rest of this manual will be using @code{kpse} as a placeholder for
the name of this variable.

@item
@findex kpathsea_set_program_name
@vindex argv[0]
Call @code{kpathsea_set_program_name} with @code{argv[0]} as the second
argument; the third argument is a string or @code{NULL}.  The third
argument is used by Kpathsea as the program name for the
@code{.@var{program}} feature of config files (@pxref{Config files}).
If the third argument is @code{NULL}, the value of the second argument
is used.  This function must be called before any other use of the
Kpathsea library.

@vindex kpse->invocation_name
@vindex kpse->invocation_short_name
@vindex kpse->program_name
@cindex error message macros
@code{kpathsea_set_program_name} always sets the variables
@code{kpse->invocation_name} and @code{kpse->invocation_short_name}.
These variables are used in the error message macros defined in
@file{kpathsea/lib.h}.  It sets the variable
@code{kpse->program_name} to the program name it uses.

@vindex KPATHSEA_DEBUG
It also initializes debugging options based on the environment
variable @code{KPATHSEA_DEBUG} (if that is set).

@cindex SELFAUTOLOC
@cindex SELFAUTODIR
@cindex SELFAUTOPARENT
@cindex symlinks, resolving
@cindex expanding symlinks
Finally, it sets the environment variables @code{SELFAUTOLOC},
@code{SELFAUTODIR} and @code{SELFAUTOPARENT} to the location, parent
and grandparent directory of the executable, removing @file{.} and
@file{..} path elements and resolving symbolic links.  These are used
in the default configuration file to allow people to invoke TeX from
anywhere.  You can use @samp{kpsewhich --expand-var=\$SELFAUTOLOC},
etc., to see the values.

@item
@vindex kpse->debug @r{variable}
@cindex debugging options, in Kpathsea-using program
Set debugging options. @xref{Debugging}.  If your program doesn't have
a debugging option already, you can define one and set
@code{kpse->debug} to the number that the user supplies (as in Dviljk
and Web2c), or you can just omit this altogether (users can always set
the @code{KPATHSEA_DEBUG} environment variable).  If you do have
runtime debugging already, you need to merge Kpathsea's options with
yours (as in Dvipsk and Xdvik).

@item
@vindex client_path @r{in @code{kpse->format_info}}
@vindex kpse->format_info
@flindex resident.c
@cindex config files, for Kpathsea-using programs
If your program has its own configuration files that can define search
paths, you should assign those paths to the @code{client_path} member in
the appropriate element of the @code{kpse->format_info} array.  (This
array is indexed by file type; see @file{tex-file.h}.)  See
@file{resident.c} in Dvipsk for an example.

@item
@findex kpathsea_init_prog
@flindex proginit.h
Call @code{kpathsea_init_prog} (see @file{proginit.c}). It's useful
for the DVI drivers, at least, but for other programs it may be
simpler to extract the parts of it that actually apply.  This does not
initialize any paths, it just looks for (and sets) certain environment
variables and other random information.  Search paths are always
initialized at the first call to find a file of a given type, not
requiring an explicit initialization call; this eliminates much
useless work, e.g., initializing the Bib@TeX{} search paths in a DVI
driver.

@item
@findex kpathsea_find_file
The routine to actually find a file of type @var{format} is
@file{kpathsea_find_file}.  You can call
@code{kpathsea_find_file} after doing only the first and second of the
initialization steps above---Kpathsea automatically reads the
@file{texmf.cnf} generic config files, looks for environment variables,
and does expansions at the first lookup.

@item
@findex kpathsea_find_glyph
To find PK and/or GF bitmap fonts, the routine
is @code{kpathsea_find_glyph}, defined in
@file{tex-glyph.h}. This returns a structure in addition to the
resultant filename, because fonts can be found in so many ways. See the
documentation in the source.

@item
Before opening a file, especially for writing, you should check if the
filename is acceptable.  See the next section (@pxref{Safe filenames}).

@item
@findex kpathsea_open_file
To actually open a file, not just return a filename, call
@code{kpathsea_open_file}.  This function takes the name to look up and a
Kpathsea file format as arguments, and returns the usual @code{FILE *}.
It always assumes the file must exist, and thus will search the disk if
necessary (unless the search path specified @samp{!!}, etc.).  In other
words, if you are looking up a VF or some other file that need not
exist, don't use this.

@item
@findex kpathsea_finish
To close the Kpathsea library instance you are using, call
@code{kpathsea_finish}.  This function closes any open log files and
frees the memory used by the instance.

@end enumerate

@cindex hash table routines
@cindex memory allocation routines
@cindex string routines
@cindex reading arbitrary-length lines
@cindex input lines, reading
@cindex lines, reading arbitrary-length
Kpathsea also provides many utility routines. Some are generic: hash
tables, memory allocation, string concatenation and copying, string
lists, reading input lines of arbitrary length, etc. Others are
filename-related: default path, tilde, and variable expansion,
@code{stat} calls, etc.

@flindex c-*.h
@pindex autoconf@r{, recommended}
The @file{c-*.h} header files can also help your program adapt to many
different systems.  You will almost certainly want to use Autoconf and
probably Automake for configuring and building your software if you use
Kpathsea; I strongly recommend using Autoconf and Automake regardless.
They are available from @url{https://gnu.org/software}.


@node Safe filenames
@section Safe filenames

@vindex openout_any
@anchor{openout_any}
@cindex trojan horse
@xref{Security}, for some general security considerations with the
@TeX{} system.

In the implementation, the main security feature to disallow writing
to potentially dangerous files is a configuration variable
@code{openout_any}. It specifies one of three levels:

@itemize
@item
@cindex unrestricted mode, for output files
When set to @samp{a} (for ``any''), no restrictions are imposed.

@item
@cindex restricted mode, for output files
When is set to @samp{r} (for ``restricted''), filenames beginning
with @samp{.} are disallowed.

@item
@cindex paranoid mode, for output files
When set to @samp{p} (for ``paranoid''), additional restrictions are
imposed.

@enumerate
@item
@vindex TEXMF_OUTPUT_DIRECTORY@r{, and paranoid output files}
@vindex TEXMFOUTPUT@r{, and paranoid output files}
First, an absolute filename must refer to a file in (or in a
subdirectory of) either the @code{TEXMF_OUTPUT_DIRECTORY} environment
variable or the @code{TEXMFOUTPUT} environment variable or
configuration file setting.

@item
@vindex TEXMFSYSVAR
@vindex TEXMFVAR
@findex luaotfload
Lua@TeX{} uses a so-called ``extended'' mode, in which the values of
@code{TEXMFVAR} and @code{TEXMFSYSVAR} are also checked for absolute
filenames.  This is done because, in practice, fundamental parts of
the Lua@LaTeX{} system (notably @code{luaotfload}) need a cache
directory, and historically the @code{TEXMF[SYS]VAR} variables are
what has been used. We neither recommend nor expect any other programs
to need this.

@item 
Finally, any attempt to go up a directory level is forbidden; that is,
paths may not contain a @samp{..} component.

@end enumerate
@end itemize

The paranoid setting is the default. Any program intended to be safely
called from @TeX{} should implement the same measures, one way or
another.  @xref{Shell escapes,,, web2c, Web2c}.

Kpathsea does not resolve @samp{..} components, or symbolic links, to
see if the final result is an acceptable directory; they are simply
forbidden.  That is, Kpathsea merely considers the value as a string,
not looking on the filesystem at all.  (However, if another program
wants to do such resolutions and check the result, that's ok; possibly
preferable.)

For backwards compatibility, @samp{y} and @samp{1} are synonyms of
@samp{a}, while @samp{n} and @samp{0} are synonyms for @samp{r}.

@findex kpathsea_out_name_ok
The function @code{kpathsea_out_name_ok}, with a filename as second
argument, returns @code{true} if that filename is acceptable to be
opened for output or @code{false} otherwise.  The Kpsewhich program
has an option (@samp{--safe-out-name}) providing a command line
interface for the check.

@findex kpathsea_out_name_ok_extended
For Lua@TeX{}'s extended mode, the function is
@code{kpathsea_out_name_ok_extended}, and the Kpsewhich option is
@samp{--safe-extended-out-name}.

@findex kpathsea_in_name_ok
@findex kpathsea_in_name_ok_extended
@vindex openin_any
Although the analogous functions @code{kpathsea_in_name_ok} (resp.@:
@code{_extended}, as well as the others below, exist to check a
filename being acceptable for reading, as of 2026, they always return
true without checking anything. This is because no other value was
useful (or used) in practice.  More comments about this are in the
default @file{texmf.cnf}, at @code{openin_any} (which variable is
defined, but is now ignored).

The functions above write a message to standard error if the usage is
forbidden (so every caller does not have to do so).  Each function has
a @code{_silent} counterpart which does not write the message; this is
what Kpsewhich calls, since messages would be counterproductive in
that case. Thus:

@findex kpathsea_out_name_ok_silent
@findex kpathsea_out_name_ok_silent_extended
@findex kpathsea_in_name_ok_silent
@findex kpathsea_in_name_ok_silent_extended

@example
kpathsea_out_name_ok_silent
kpathsea_out_name_ok_silent_extended
kpathsea_in_name_ok_silent
kpathsea_in_name_ok_silent_extended
@end example

Furthermore, there are @code{kpse_...} versions of all the above
functions (as usual), with the default library instance implicitly
passed as the first argument.  Lua@TeX{} provides both @code{kpse.*}
and @code{kpathsea.*} bindings, so it's good to always have both.
	
Sorry for the combinatorial explosion, but we hope no further options
will ever be needed.  If so, we'll likely provide a more generic
interface as well as the above.


@node Program-specific files
@section Program-specific files

Many programs will need to find some configuration files.  Kpathsea
contains some support to make it easy to place them in their own
directories.  The Standard @TeX{} directory structure (@pxref{Top,,
Introduction, tds, A Directory Structure for @TeX{} files}), specifies
that such files should go into a subdirectory named after the program,
like @samp{texmf/ttf2pk}.

Two formats, @samp{kpse_program_text_format} and
@samp{kpse_program_binary_format}, use @code{.:$TEXMF/@var{program}//}
as their compiled-in search path.  To override this default, you can
use the variable @code{@var{PROGRAM}INPUTS} in the environment and/or
@samp{texmf.cnf}.  That is to say, the name of the variable is
constructed by converting the name of the program to upper case, and
appending @code{INPUTS}.

The only difference between these two formats is whether
@code{kpathsea_open_file} will open the files it finds in text or binary
mode.


@node Programming with config files
@section Programming with config files

@cindex programming with config files
@cindex config files, programming with

You can (and probably should) use the same @code{texmf.cnf}
configuration file that Kpathsea uses for your program.  This helps
installers by keeping all configuration in one place.

@findex kpathsea_var_value
@flindex variable.h
@vindex shell_escape@r{, example for code}
To retrieve a value for a configuration variable @var{var}, the best
way is to call @code{kpathsea_var_value} on the string
@code{@var{var}}.  This will look first for an environment variable
@var{var}, then a config file value.  The result will be the value
found or @samp{NULL}.  This function is declared in
@file{kpathsea/variable.h}.  For an example, see the
@code{shell_escape} code in @file{web2c/lib/texmfmp.c}.

The routine to do full variable and tilde expansion of an arbitrary
string in the context of a search path (as opposed to simply
retrieving a value) is @code{kpathsea_var_expand}, also declared in
@file{kpathsea/variable.h}.  However, it's generally only necessary to
set the search path structure components as explained in the previous
section instead of using this directly.  Because of its usage with any
input string, undefined @code{$FOO} constructs in the argument to
@code{kpathsea_var_expand} are returned literally (@code{"$FOO"}),
while undefined @code{$@{FOO@}} constructs are expanded to the empty
string.

@findex kpathsea_cnf_get
@flindex cnf.h
If for some reason you want to retrieve a value @emph{only} from a
config file, not automatically looking for a corresponding environment
variable, call @code{kpathsea_cnf_get} (declared in @file{kpathsea/cnf.h})
with the string @var{var}.

No initialization calls are needed.


@node Reporting bugs
@chapter Reporting bugs

@cindex reporting bugs
@cindex bugs, reporting

@flindex tex-k@@tug.org @r{(bug address)}
@cindex bug address
If you have problems or suggestions, please report them to
@email{tex-k@@tug.org} using the bug checklist below.

Please report bugs in the documentation; not only factual errors or
inconsistent behavior, but unclear or incomplete explanations, typos,
wrong fonts, @dots{}

@menu
* Bug checklist::       What to include in a good bug report.
* Mailing lists::       Joining the bugs or announcements mailing lists.
* Debugging::           Analyzing runtime problems.
* Logging::             Recording searches.
* Common problems::     When things go wrong.
@end menu


@node Bug checklist
@section Bug checklist

@cindex checklist for bug reports
@cindex bug checklist

Before reporting a bug, please check below to be sure it isn't already
known (@pxref{Common problems}).

Bug reports should be sent via electronic mail to
@email{tex-k@@tug.org}.

The general principle is that a good bug report includes all the
information necessary for reproduction.  Therefore, to enable
investigation, your report should include the following:

@itemize @bullet
@item
@cindex version numbers, determining
The version number(s) of the program(s) involved, and of Kpathsea
itself.  You can get the former by giving a sole option @samp{--version}
to the program, and the latter by running @samp{kpsewhich --version}.
The @file{NEWS} and @file{ChangeLog} files also contain the version
number.

@item
@pindex uname
The hardware, operating system (including version), compiler, and
@code{make} program you are using (the output of @code{uname -a} is a
start on the first two, though incomplete).

@item
@flindex config.log
Any options you gave to @code{configure}.  This is recorded in the
@file{config.status} files.

@cindex configuration bugs
@flindex config.status
If you are reporting a bug in @samp{configure} itself, it's probably
system-dependent, and it will be unlikely the maintainers can do
anything useful if you merely report that thus-and-such is broken.
Therefore, you need to do some additional work: for some bugs, you can
look in the file @file{config.log} where the test that failed should
appear, along with the compiler invocation and source program in
question.  You can then compile it yourself by hand, and discover why
the test failed.  Other @samp{configure} bugs do not involve the
compiler; in that case, the only recourse is to inspect the
@code{configure} shell script itself, or the Autoconf macros that
generated @code{configure}.

@item
The log of all debugging output, if the bug is in path searching.  You
can get this by setting the environment variable @code{KPATHSEA_DEBUG}
to @samp{-1} before running the program.  Please look at the log
yourself to make sure the behavior is really a bug before reporting it;
perhaps ``old'' environment variable settings are causing files not to
be found, for example.

@item
The contents of any input files necessary to reproduce the bug.  For
bugs in DVI-reading programs, for example, this generally means a DVI
file (and any EPS or other files it uses)---@TeX{} source files are
helpful, but the DVI file is required, because that's the actual
program input.

@item
@cindex context diff
@cindex sending patches
@flindex ChangeLog @r{entry}
If you are sending a patch (do so if you can!), please do so in the form
of a context diff (@samp{diff -c}) against the original distribution
source.  Any other form of diff is either not as complete or harder for
me to understand.  Please also include a @file{ChangeLog} entry.

@item
@cindex stack trace
@cindex debugger
@cindex crashes, reporting
@cindex core dumps, reporting
@cindex null pointers, dereferencing
@pindex gdb@r{, recommended}
If the bug involved is an actual crash (i.e., core dump), it is easy
and useful to include a stack trace from a debugger (I recommend the
GNU debugger GDB (@url{https://gnu.org/software/gdb}).  If the
cause is apparent (a @code{NULL} value being dereferenced, for
example), please send the details along.  If the program involved is
@TeX{} or Metafont, and the crash is happening at apparently-sound
code, however, the bug may well be in the compiler, rather than in the
program or the library (@pxref{TeX or Metafont failing,, @TeX{} or
Metafont failing}).

@item
Any additional information that will be helpful in reproducing,
diagnosing, or fixing the bug.
@end itemize


@node Mailing lists
@section Mailing lists

@cindex mailing lists
@cindex bug mailing list
@cindex announcement mailing list

@flindex tex-k@@tug.org
Web2c and Kpathsea in general are discussed on the mailing list
@email{tex-k@@tug.org}.  You can subscribe and peruse the archives on
the web @url{https://lists.tug.org/tex-k}.

You do not need to join to submit a report, nor will it affect whether
you get a response.  Be aware that large data files are sometimes
included in bug reports.  If this is a problem for you, do not join
the list.

If you are looking for general @TeX{} help, such as how to install a
full @TeX{} system or how to use @LaTeX{}, please see
@url{https://tug.org/begin.html}.


@node Debugging
@section Debugging

@cindex debugging
@cindex runtime debugging
@cindex options for debugging

@vindex kpse->debug
@flindex debug.h
Kpathsea provides a number of runtime debugging options, detailed below
by their names and corresponding numeric values.  When the files you
expect aren't being found, the thing to do is enable these options and
examine the output.

You can set these with some runtime argument (e.g., @samp{-d}) to the
program; in that case, you should use the numeric values described in
the program's documentation (which, for Dvipsk and Xdvik, are different
than those below).  It's best to give the @samp{-d} (or whatever) option
first, for maximal output.  Dvipsk and Xdvik have additional
program-specific debugging options as well.

@vindex KPATHSEA_DEBUG
@vindex kpse->debug
You can also set the environment variable @code{KPATHSEA_DEBUG}; in this
case, you should use the numbers below.  If you run the program under a
debugger and set the instance variable @code{kpse->debug}, also use the numbers
below.

@kindex -1 @r{debugging value}
In any case, by far the simplest value to use is @samp{-1}, which will
turn on all debugging output.  This is usually better than guessing
which particular values will yield the output you need.

@cindex debugging output
@cindex standard error and debugging output
Debugging output always goes to standard error, so you can redirect it
easily.  For example, in Bourne-compatible shells:
@example
dvips -d -1 @dots{} 2>/tmp/debug
@end example

@cindex Kpsewhich, and debugging
It is sometimes helpful to run the standalone Kpsewhich utility
(@pxref{Invoking kpsewhich}), instead of the original program.

@cindex numeric debugging values
In any case, you cannot use the names below; you must always use
somebody's numbers.  (Sorry.)  To set more than one option, just sum
the corresponding numbers.

@vtable @code
@item KPSE_DEBUG_STAT @r{(1)}
Report @samp{stat}(2) calls. This is useful for verifying that your
directory structure is not forcing Kpathsea to do many additional file
tests (@pxref{Slow path searching}, and @pxref{Subdirectory
expansion}). If you are using an up-to-date @file{ls-R} database
(@pxref{Filename database}), this should produce no output unless a
nonexistent file that must exist is searched for.

@item KPSE_DEBUG_HASH @r{(2)}
Report lookups in all hash tables: @file{ls-R} and @file{aliases}
(@pxref{Filename database}); font aliases (@pxref{Fontmap}); and config
file values (@pxref{Config files}).  Useful when expected values are not
being found, e.g.., file searches are looking at the disk instead of
using @file{ls-R}.

@item KPSE_DEBUG_FOPEN @r{(4)}
@findex fopen@r{, redefined}
Report file openings and closings. Especially useful when your system's
file table is full, for seeing which files have been opened but never
closed. In case you want to set breakpoints in a debugger: this works by
redefining @samp{fopen} (@samp{fclose}) to be @samp{kpse_fopen_trace}
(@samp{kpse_fclose_trace}).

@item KPSE_DEBUG_PATHS @r{(8)}
@tindex kpse_format_info_type
Report general path information for each file type Kpathsea is asked to
search. This is useful when you are trying to track down how a
particular path got defined---from @file{texmf.cnf}, @file{config.ps},
an environment variable, the compile-time default, etc.  This is the
contents of the @code{kpse_format_info_type} structure defined in
@file{tex-file.h}.

@item KPSE_DEBUG_EXPAND @r{(16)}
Report the directory list corresponding to each path element Kpathsea
searches. This is only relevant when Kpathsea searches the disk, since
@file{ls-R} searches don't look through directory lists in this way.

@item KPSE_DEBUG_SEARCH @r{(32)}
Report on each file search: the name of the file searched for, the path
searched in, whether or not the file must exist (when drivers search for
@file{cmr10.vf}, it need not exist), and whether or not we are
collecting all occurrences of the file in the path (as with, e.g.,
@file{texmf.cnf} and @file{texfonts.map}), or just the first (as with
most lookups).  This can help you correlate what Kpathsea is doing with
what is in your input file.

@item KPSE_DEBUG_VARS @r{(64)}
Report the value of each variable Kpathsea looks up.  This is useful for
verifying that variables do indeed obtain their correct values.

@item GSFTOPK_DEBUG @r{(128)}
Activates debugging printout specific to @code{gsftopk} program.

@item MAKETEX_DEBUG @r{(512)}
If you use the optional @code{mktex} programs instead of the
traditional shell scripts, this will report the name of the site file
(@file{mktex.cnf} by default) which is read, directories created by
@code{mktexdir}, the full path of the @file{ls-R} database built by
@code{mktexlsr}, font map searches, @code{MT_FEATURES} in effect,
parameters from @code{mktexnam}, filenames added by
@code{mktexupd}, and some subsidiary commands run by the programs.

@item MAKETEX_FINE_DEBUG @r{(1024)}
When the optional @code{mktex} programs are used, this will print
additional debugging info from functions internal to these programs.
@end vtable

@cindex @samp{kdebug:}
@vindex hash_summary_only @r{variable for debugging}
@cindex hash table buckets, printing
Debugging output from Kpathsea is always written to standard error, and
begins with the string @samp{kdebug:}. (Except for hash table buckets,
which just start with the number, but you can only get that output
running under a debugger. See comments at the @code{hash_summary_only}
variable in @file{kpathsea/db.c}.)


@node Logging
@section Logging

@cindex log file

@cindex logging successful searches
@cindex recording successful searches
@cindex usage patterns, finding
@cindex disk usage, reducing
Kpathsea can record the time and filename found for each successful
search.  This may be useful in finding good candidates for deletion when
your filesystem is full, or in discovering usage patterns
at your site.

@vindex TEXMFLOG
To do this, define the environment or config file variable
@code{TEXMFLOG}.  The value is the name of the file to append the
information to.  The file is created if it doesn't exist, and appended
to if it does.

@cindex epoch, seconds since
@findex time @r{system call}
Each successful search turns into one line in the log file: two words
separated by a space.  The first word is the time of the search, as the
integer number of seconds since ``the epoch'', i.e., UTC midnight 1
January 1970 (more precisely, the result of the @code{time} system
call).  The second word is the filename.

For example, after @code{setenv TEXMFLOG /tmp/log}, running Dvips on
@file{story.dvi} appends the following lines:

@example
774455887 /usr/local/share/texmf/dvips/config.ps
774455887 /usr/local/share/texmf/dvips/psfonts.map
774455888 /usr/local/share/texmf/dvips/texc.pro
774455888 /usr/local/share/texmf/fonts/pk/ljfour/public/cm/cmbx10.600pk
774455889 /usr/local/share/texmf/fonts/pk/ljfour/public/cm/cmsl10.600pk
774455889 /usr/local/share/texmf/fonts/pk/ljfour/public/cm/cmr10.600pk
774455889 /usr/local/share/texmf/dvips/texc.pro
@end example

@cindex privacy, semblance of
@noindent Only filenames that are absolute are recorded, to preserve
some semblance of privacy.

In addition to this Kpathsea-specific logging, @command{pdftex}
provides an option @option{-recorder} to write the names of all files
accessed during a run to the file @file{@var{basefile}.fls}.

Finally, most systems provide a general tool to output each system
call, thus including opening and closing files.  It might be named
@command{strace}, @command{truss}, @command{struss}, or something
else.


@node Common problems
@section Common problems

@cindex common problems
@cindex problems, common
@cindex FAQ, Kpathsea

Here are some common problems with configuration, compilation, linking,
execution, @dots{}

@menu
* Unable to find files::        If your program can't find fonts (or whatever).
* Slow path searching::         If it takes forever to find anything.
* Unable to generate fonts::    If mktexpk fails.
* TeX or Metafont failing::     Likely compiler bugs.
@end menu

@node Unable to find files
@subsection Unable to find files

@cindex unable to find files
@cindex files, unable to find

If a program complains it cannot find fonts (or other input files), any
of several things might be wrong.  In any case, you may find the
debugging options helpful.  @xref{Debugging}.

@itemize @bullet
@item
Perhaps you simply haven't installed all the necessary files; the basic
fonts and input files are distributed separately from the programs.
@xref{unixtex.ftp}.

@item
@flindex /etc/profile
@cindex environment variables, old
You have (perhaps unknowingly) told Kpathsea to use search paths that
don't reflect where the files actually are.  One common cause is having
environment variables set from a previous installation, thus overriding
what you carefully set in @file{texmf.cnf} (@pxref{Supported file
formats}).  System @file{/etc/profile} or other files such may be the
culprit.

@item
@cindex symbolic links not found
@cindex leaf directories wrongly guessed
Your files reside in a directory that is only pointed to via a symbolic
link within a leaf directory, and is not listed in @file{ls-R}.

Unfortunately, Kpathsea's subdirectory searching has a problematic
deficiency: If a directory @var{d} being searched for subdirectories
contains symbolic links to other directories (and possibly other plain
files or symlinks), but no true subdirectories, by default @var{d}
will be considered a leaf directory, i.e., the symbolic links will not
be followed.  @xref{Subdirectory expansion}.

You can work around this problem by creating an empty dummy subdirectory
in @var{d}. Then @var{d} will no longer be a leaf, and the symlinks will
be followed.

Another workaround is to set the configuration variable
@code{kpse_ignore_nlink_for_leaf} to 1.  Then Kpathsea will look at
all entries in all directories in determining whether they are
(symlinks to) subdirectories. This is not the default because it is
considerably expensive to consider the contents of every leaf directory.

The directory immediately followed by the @samp{//} in the path
specification is always searched for subdirectories, even if it is a
leaf.  Presumably you would not have asked for the directory to be
searched for subdirectories if you didn't want it to be.

@item
If the fonts (or whatever) don't already exist, @code{mktexpk} (or
@code{mktexmf} or @code{mktextfm}) will try to create them.  If
these rather complicated shell scripts fail, you'll eventually get an
error message saying something like @samp{Can't find font
@var{fontname}}. The best solution is to fix (or at least report) the
bug in @code{mktexpk}; the workaround is to generate the necessary
fonts by hand with Metafont, or to grab them from a CTAN site
(@pxref{unixtex.ftp}).

@item
There is a bug in the library. @xref{Reporting bugs}.
@end itemize


@node Slow path searching
@subsection Slow path searching

@cindex excessive startup time
@cindex slow startup time
@cindex startup time, excessive

If your program takes an excessively long time to find fonts or other
input files, but does eventually succeed, here are some possible culprits:

@itemize @bullet
@item
Most likely, you just have a lot of directories to search, and that
takes a noticeable time. The solution is to create and maintain a
separate @file{ls-R} file that lists all the files in your main @TeX{}
hierarchy.  @xref{Filename database}.  Kpathsea always uses @file{ls-R}
if it's present; there's no need to recompile or reconfigure any of the
programs.

@item
Your recursively-searched directories (e.g.,
@file{/usr/local/share/texmf/fonts//}), contain a mixture of files and
directories. This prevents Kpathsea from using a useful optimization
(@pxref{Subdirectory expansion}).

It is best to have only directories (and perhaps a @file{README}) in the
upper levels of the directory structure, and it's very important to have
@emph{only} files, and no subdirectories, in the leaf directories where
the dozens of TFM, PK, or whatever files reside.
@end itemize

In any case, you may find the debugging options helpful in determining
precisely when the disk or network is being pounded.  @xref{Debugging}.


@node Unable to generate fonts
@subsection Unable to generate fonts

@cindex unable to generate fonts
@cindex font generation failures

Metafont outputs fonts in bitmap format, tuned for a particular
device at a particular resolution, in order to allow for the
highest-possible quality of output.  Some DVI-to-whatever programs,
such as Dvips, try to generate these on the fly when they are needed,
but this generation may fail in several cases.

@cindex @code{mktexpk} can't guess mode
If @code{mktexpk} runs, but fails with this error:
@example
mktexpk: Can't guess mode for @var{nnn} dpi devices.
mktexpk: Use a config file to specify the mode, or update me.
@end example
you need to ensure the resolution and mode match; just
specifying the resolution, as in @code{-D 360}, is not enough.

You can specify the mode name with the @code{-mode} option on the
Dvips command line, or in a Dvips configuration file (@pxref{Config
files,,, dvips, Dvips}), such as @file{config.ps} in your document
directory, @file{~/.dvipsrc} in your home directory, or in a system
directory (again named @file{config.ps}).  (Other drivers use other
files, naturally.)

For example, if you need 360@dmn{dpi} fonts, you could include this in
a configuration file:
@example
D 360
M lqmed
@end example

@cindex Metafont using the wrong device
@cindex device, wrong
If Metafont runs, but generates fonts at the wrong resolution or for
the wrong device, most likely @code{mktexpk}'s built-in guess for the
mode is wrong, and you should override it as above.

See @url{https://ctan.org/pkg/modes} for a list of resolutions and mode
names for most devices (additional submissions are welcome).

@flindex .2602gf
@flindex 2602gf
@cindex Metafont making too-large fonts
@cindex proof mode
@cindex online Metafont display, spurious
If Metafont runs but generates fonts at a resolution of 2602@dmn{dpi}
(and prints out the name of each character as well as just a character
number, and maybe tries to display the characters), then your Metafont
base file probably hasn't been made properly.  (It's using the default
@code{proof} mode, instead of an actual device mode.)  To make a proper
@file{plain.base}, assuming the local mode definitions are contained in
a file @file{modes.mf}, run the following command (assuming Unix):

@example
inimf "plain; input modes; dump"
@end example

@noindent
@flindex plain.base
Then copy the @file{plain.base} file from the current directory to where
the base files are stored on your system
(@file{/usr/local/share/texmf/web2c} by default), and make a link
(either hard or soft) from @file{plain.base} to @file{mf.base} in that
directory.
@xref{inimf invocation,,, web2c, Web2c}.

@cindex Metafont installation
If @code{mf} is a command not found at all by @code{mktexpk}, then you
need to install Metafont (@pxref{unixtex.ftp}).


@node TeX or Metafont failing
@subsection @TeX{} or Metafont failing

@cindex @TeX{} failures
@cindex Metafont failures
@cindex compiler bugs
If @TeX{} or Metafont get a segmentation fault or otherwise fail while
running a normal input file, the problem is usually a compiler bug
(unlikely as that may sound).  Even if the trip and trap tests are
passed, problems may lurk.  Optimization occasionally causes trouble in
programs other than @TeX{} and Metafont themselves, too.

@cindex optimization caveat
For a workaround, if you enabled any optimization flags, it's best to
omit optimization entirely.  In any case, the way to find the facts is
to run the program under the debugger and see where it's failing.

@cindex GNU C compiler bugs
@cindex system C compiler bugs
Also, if you have trouble with a system C compiler, I advise trying the
GNU C compiler. And vice versa, unfortunately; but in that case I also
recommend reporting a bug to the GCC mailing list; see @ref{Bugs,,, gcc,
Using and Porting GNU CC}.

@cindex compiler bugs, finding
To report compiler bugs effectively requires perseverance and
perspicacity: you must find the miscompiled line, and that usually
involves delving backwards in time from the point of error, checking
through @TeX{}'s (or whatever program's) data structures.  Good luck.


@node Index
@unnumbered Index

@printindex cp

@bye
