diff options
Diffstat (limited to 'Build/source/texk/kpathsea/doc/kpathsea.texi')
-rw-r--r-- | Build/source/texk/kpathsea/doc/kpathsea.texi | 74 |
1 files changed, 48 insertions, 26 deletions
diff --git a/Build/source/texk/kpathsea/doc/kpathsea.texi b/Build/source/texk/kpathsea/doc/kpathsea.texi index db619f50129..8fdb387fff1 100644 --- a/Build/source/texk/kpathsea/doc/kpathsea.texi +++ b/Build/source/texk/kpathsea/doc/kpathsea.texi @@ -3,7 +3,7 @@ @settitle Kpathsea: A library for path searching @set version 6.3.2 -@set month-year August 2019 +@set month-year December 2019 @copying This file documents the Kpathsea library for path searching. @@ -445,6 +445,12 @@ 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. @@ -652,7 +658,7 @@ start a comment. Examples: @example % this is a comment -var = a%b % but the value of var will be "a%b". +var = a%b % but the value of var will be "a%b" @end example @item @@ -668,7 +674,7 @@ 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 must look like +@item Each remaining line will look like: @example @var{variable} @r{[}. @var{progname}@r{]} @r{[}=@r{]} @var{value} @@ -681,6 +687,7 @@ lines is not ignored. 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) @@ -691,15 +698,21 @@ variable or other expansions. @item @cindex right-hand side of variable assignments -@var{value} may contain any characters except @samp{%} and @samp{@@}. -(These restrictions are only necessary because of the processing done -on @file{texmf.cnf} at build time, so you can stick those characters -in after installation if you have to.) The -@samp{$@var{var}.@var{prog}} feature is not available on the +Considered as strings, @var{value} may contain any character. +However, in practice most @file{texmf.cnf} values are related to path +expansion, and since various special characters are used in expansion, +such as braces and commas, they cannot be used in directory names. + +The @samp{$@var{var}.@var{prog}} feature is not available on the right-hand side; instead, you must use an additional variable (see -below for example). A @samp{;} in @var{value} is translated to -@samp{:} if running under Unix; this is useful to write a single -@file{texmf.cnf} which can be used under both Unix and Windows. +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 @@ -721,14 +734,15 @@ TEXINPUTS.latex = $latex2e_inputs @cindex shell scripts as configuration files @cindex configuration files as shell scripts. -This format has obvious similarities to Bourne shell scripts---change -the comment character to @code{#}, disallow spaces around the -@code{=}, and get rid of the @code{.@var{name}} convention, and it -could be run through the shell. However, there seemed little -advantage in this, since all the information would have to passed back -to Kpathsea and parsed there anyway, since the @code{sh} process -couldn't affect its parent's environment. - +This format has some similarity to Bourne shell scripts---change the +comment character to @code{#}, disallow spaces around the @code{=}, +and get rid of the @code{.@var{name}} convention, and it could be run +through the shell. However, there seemed little advantage in this, +since all the information would have to passed back to Kpathsea and +parsed there anyway, since the @code{sh} process couldn't affect its +parent's environment. + +@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{.} @@ -739,6 +753,15 @@ an empty value for @code{var} running under the program named 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}. @@ -1024,11 +1047,11 @@ You can disable the trick by undefining @code{ST_NLINK_TRICK} in Unfortunately, in some cases files in leaf directories are @code{stat}'d: 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 +@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 can find a way to @emph{solve} the problem, please -let me know. +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 @@ -1217,7 +1240,7 @@ happens with the elements of the leaf directory. Kpathsea goes to some lengths to minimize disk accesses for searches (@pxref{Subdirectory expansion}). Nevertheless, in practice searching -each possible directory in typical @TeX{} installations takes an +every possible directory in typical @TeX{} installations takes an excessively long time. Therefore, Kpathsea can use an externally-built @dfn{filename @@ -1225,8 +1248,7 @@ 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}. This can be helpful to adapt -to ``8.3'' filename conventions in source files. +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}. |