(make.info.gz) Install Command Categories

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 14.6 Install Command Categories
 ===============================
 
 When writing the `install' target, you must classify all the commands
 into three categories: normal ones, "pre-installation" commands and
 "post-installation" commands.
 
    Normal commands move files into their proper places, and set their
 modes.  They may not alter any files except the ones that come entirely
 from the package they belong to.
 
    Pre-installation and post-installation commands may alter other
 files; in particular, they can edit global configuration files or data
 bases.
 
    Pre-installation commands are typically executed before the normal
 commands, and post-installation commands are typically run after the
 normal commands.
 
    The most common use for a post-installation command is to run
 `install-info'.  This cannot be done with a normal command, since it
 alters a file (the Info directory) which does not come entirely and
 solely from the package being installed.  It is a post-installation
 command because it needs to be done after the normal command which
 installs the package's Info files.
 
    Most programs don't need any pre-installation commands, but we have
 the feature just in case it is needed.
 
    To classify the commands in the `install' rule into these three
 categories, insert "category lines" among them.  A category line
 specifies the category for the commands that follow.
 
    A category line consists of a tab and a reference to a special Make
 variable, plus an optional comment at the end.  There are three
 variables you can use, one for each category; the variable name
 specifies the category.  Category lines are no-ops in ordinary execution
 because these three Make variables are normally undefined (and you
 _should not_ define them in the makefile).
 
    Here are the three possible category lines, each with a comment that
 explains what it means:
 
              $(PRE_INSTALL)     # Pre-install commands follow.
              $(POST_INSTALL)    # Post-install commands follow.
              $(NORMAL_INSTALL)  # Normal commands follow.
 
    If you don't use a category line at the beginning of the `install'
 rule, all the commands are classified as normal until the first category
 line.  If you don't use any category lines, all the commands are
 classified as normal.
 
    These are the category lines for `uninstall':
 
              $(PRE_UNINSTALL)     # Pre-uninstall commands follow.
              $(POST_UNINSTALL)    # Post-uninstall commands follow.
              $(NORMAL_UNINSTALL)  # Normal commands follow.
 
    Typically, a pre-uninstall command would be used for deleting entries
 from the Info directory.
 
    If the `install' or `uninstall' target has any dependencies which
 act as subroutines of installation, then you should start _each_
 dependency's commands with a category line, and start the main target's
 commands with a category line also.  This way, you can ensure that each
 command is placed in the right category regardless of which of the
 dependencies actually run.
 
    Pre-installation and post-installation commands should not run any
 programs except for these:
 
      [ basename bash cat chgrp chmod chown cmp cp dd diff echo
      egrep expand expr false fgrep find getopt grep gunzip gzip
      hostname install install-info kill ldconfig ln ls md5sum
      mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee
      test touch true uname xargs yes
 
    The reason for distinguishing the commands in this way is for the
 sake of making binary packages.  Typically a binary package contains
 all the executables and other files that need to be installed, and has
 its own method of installing them--so it does not need to run the normal
 installation commands.  But installing the binary package does need to
 execute the pre-installation and post-installation commands.
 
    Programs to build binary packages work by extracting the
 pre-installation and post-installation commands.  Here is one way of
 extracting the pre-installation commands (the `-s' option to `make' is
 needed to silence messages about entering subdirectories):
 
      make -s -n install -o all \
            PRE_INSTALL=pre-install \
            POST_INSTALL=post-install \
            NORMAL_INSTALL=normal-install \
        | gawk -f pre-install.awk
 
 where the file `pre-install.awk' could contain this:
 
      $0 ~ /^(normal-install|post-install)[ \t]*$/ {on = 0}
      on {print $0}
      $0 ~ /^pre-install[ \t]*$/ {on = 1}
 

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