gnulib/build-aux/relocatable.pl.in

# The functions in this file provide support for relocatability of
# Perl scripts.  They should be included near the beginning of each
# Perl script in a relocatable program, by adding @relocatable_pl@
# and causing the script to be expanded with AC_CONFIG_FILES.  A
# small amount of additional code must be added and adapted to the
# package by hand; see doc/relocatable-maint.texi (in Gnulib) for
# details.
#
# This code is based on relocatable.sh.in, and design changes (and
# bugs) should probably be cross-checked with it.
#
# Copyright (C) 2013, 2015-2020 Free Software Foundation, Inc.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.
#

use Config;
use File::Basename;
use File::Spec::Functions;
use Cwd 'realpath';

# Support for relocatability.
sub find_curr_installdir {
  # Determine curr_installdir, even taking into account symlinks.
  my $curr_executable = $0;
  my $basename = basename($0);
  if ($curr_executable eq $basename) {
    LOOP: for my $dir (split /$Config{path_sep}/, $ENV{PATH}) {
      $dir = "." unless $dir;
      for my $ext ('') {
        my $filename = catfile($dir, "$curr_executable$ext");
        if (-f $filename) {
          $curr_executable = $filename;
          last LOOP;
        }
      }
    }
  }
  # Resolve symlinks and canonicalize.
  return realpath(dirname($curr_executable));
}
sub find_prefixes {
  # Compute the original/current installation prefixes by stripping the
  # trailing directories off the original/current installation directories.
  my ($orig_installprefix, $curr_installprefix) = @_;
  my $orig_last = basename($orig_installprefix);
  my $curr_last = basename($curr_installprefix);
  if ($orig_last && $curr_last && $orig_last eq $curr_last) {
    $orig_installprefix = dirname($orig_installprefix);
    $curr_installprefix = dirname($curr_installprefix);
  }
  return $orig_installprefix, $curr_installprefix;
}