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(autoconf.info)Configuration Actions

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Taking Configuration Actions
============================

   `configure' is designed so that it appears to do everything itself,
but there is actually a hidden slave: `config.status'.  `configure' is
in charge of examining your system, but it is `config.status' that
actually takes the proper actions based on the results of `configure'.
The most typical task of `config.status' is to _instantiate_ files.

   This section describes the common behavior of the four standard
instantiating macros: `AC_CONFIG_FILES', `AC_CONFIG_HEADERS',
`AC_CONFIG_COMMANDS' and `AC_CONFIG_LINKS'.  They all have this
prototype:

     AC_CONFIG_FOOS(TAG..., [COMMANDS], [INIT-CMDS])

where the arguments are:

TAG...
     A whitespace-separated list of tags, which are typically the names
     of the files to instantiate.

     You are encouraged to use literals as TAGS.  In particular, you
     should avoid

          ... && my_foos="$my_foos fooo"
          ... && my_foos="$my_foos foooo"
          AC_CONFIG_FOOS($my_foos)

     and use this instead:

          ... && AC_CONFIG_FOOS(fooo)
          ... && AC_CONFIG_FOOS(foooo)

     The macros `AC_CONFIG_FILES' and `AC_CONFIG_HEADERS' use special
     TAGs: they may have the form `OUTPUT' or `OUTPUT:INPUTS'. The file
     OUTPUT is instantiated from its templates, INPUTS (defaulting to
     `OUTPUT.in').

     For instance
     `AC_CONFIG_FILES(Makefile:boiler/top.mk:boiler/bot.mk)' asks for
     the creation of `Makefile' that will be the expansion of the
     output variables in the concatenation of `boiler/top.mk' and
     `boiler/bot.mk'.

     The special value `-' might be used to denote the standard output
     when used in OUTPUT, or the standard input when used in the
     INPUTS.  You most probably don't need to use this in
     `configure.ac', but it is convenient when using the command line
     interface of `./config.status', see *Note config.status
     Invocation::, for more details.

     The INPUTS may be absolute or relative filenames.  In the latter
     case they are first looked for in the build tree, and then in the
     source tree.

COMMANDS
     Shell commands output literally into `config.status', and
     associated with a tag that the user can use to tell `config.status'
     which the commands to run.  The commands are run each time a TAG
     request is given to `config.status'; typically, each time the file
     `TAG' is created.

     The variable set during the execution of `configure' are _not_
     available here: you first need to set them via the INIT-CMDS.
     Nonetheless the following variables are precomputed:

    `srcdir'
          The path from the top build directory to the top source
          directory.  This is what `configure''s option `--srcdir' sets.

    `ac_top_srcdir'
          The path from the current build directory to the top source
          directory.

    `ac_top_builddir'
          The path from the current build directory to the top build
          directory.  It can be empty, or else ends with a slash, so
          that you may concatenate it.

    `ac_srcdir'
          The path from the current build directory to the
          corresponding source directory.

     The "current" directory refers to the directory (or
     pseudo-directory) containing the input part of TAGS.  For
     instance, running

          AC_CONFIG_COMMANDS([deep/dir/out:in/in.in], [...], [...])

     with `--srcdir=../package' produces the following values:

          # Argument of --srcdir
          srcdir='../package'
          # Reversing deep/dir
          ac_top_builddir='../../'
          # Concatenation of $ac_top_builddir and srcdir
          ac_top_srcdir='../../../package'
          # Concatenation of $ac_top_srcdir and deep/dir
          ac_srcdir='../../../package/deep/dir'

     independently of `in/in.in'.

INIT-CMDS
     Shell commands output _unquoted_ near the beginning of
     `config.status', and executed each time `config.status' runs
     (regardless of the tag).  Because they are unquoted, for example,
     `$var' will be output as the value of `var'.  INIT-CMDS is
     typically used by `configure' to give `config.status' some
     variables it needs to run the COMMANDS.

     You should be extremely cautious in your variable names: all the
     INIT-CMDS share the same name space and may overwrite each other
     in unpredictable ways.  Sorry...

   All these macros can be called multiple times, with different TAGs,
of course!