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# Copyright © 2007-2011 Raphaël Hertzog <>
# Copyright © 2011 Linaro Limited
# 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 2 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
# 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 <>.
package Dpkg::Path;
use strict;
use warnings;
our $VERSION = "1.02";
use base qw(Exporter);
use File::Spec;
use Cwd qw(realpath);
use Dpkg::Arch qw(get_host_arch debarch_to_debtriplet);
use Dpkg::IPC;
our @EXPORT_OK = qw(get_pkg_root_dir relative_to_pkg_root
guess_pkg_root_dir check_files_are_the_same
resolve_symlink canonpath find_command
get_control_path find_build_file);
=encoding utf8
=head1 NAME
Dpkg::Path - some common path handling functions
It provides some functions to handle various path.
=head1 METHODS
=over 8
=item get_pkg_root_dir($file)
This function will scan upwards the hierarchy of directory to find out
the directory which contains the "DEBIAN" sub-directory and it will return
its path. This directory is the root directory of a package being built.
If no DEBIAN subdirectory is found, it will return undef.
sub get_pkg_root_dir($) {
my $file = shift;
$file =~ s{/+$}{};
$file =~ s{/+[^/]+$}{} if not -d $file;
while ($file) {
return $file if -d "$file/DEBIAN";
last if $file !~ m{/};
$file =~ s{/+[^/]+$}{};
return undef;
=item relative_to_pkg_root($file)
Returns the filename relative to get_pkg_root_dir($file).
sub relative_to_pkg_root($) {
my $file = shift;
my $pkg_root = get_pkg_root_dir($file);
if (defined $pkg_root) {
$pkg_root .= "/";
return $file if ($file =~ s/^\Q$pkg_root\E//);
return undef;
=item guess_pkg_root_dir($file)
This function tries to guess the root directory of the package build tree.
It will first use get_pkg_root_dir(), but it will fallback to a more
imprecise check: namely it will use the parent directory that is a
sub-directory of the debian directory.
It can still return undef if a file outside of the debian sub-directory is
sub guess_pkg_root_dir($) {
my $file = shift;
my $root = get_pkg_root_dir($file);
return $root if defined $root;
$file =~ s{/+$}{};
$file =~ s{/+[^/]+$}{} if not -d $file;
my $parent = $file;
while ($file) {
$parent =~ s{/+[^/]+$}{};
last if not -d $parent;
return $file if check_files_are_the_same("debian", $parent);
$file = $parent;
last if $file !~ m{/};
return undef;
=item check_files_are_the_same($file1, $file2, $resolve_symlink)
This function verifies that both files are the same by checking that the device
numbers and the inode numbers returned by stat()/lstat() are the same. If
$resolve_symlink is true then stat() is used, otherwise lstat() is used.
sub check_files_are_the_same($$;$) {
my ($file1, $file2, $resolve_symlink) = @_;
return 0 if ((! -e $file1) || (! -e $file2));
my (@stat1, @stat2);
if ($resolve_symlink) {
@stat1 = stat($file1);
@stat2 = stat($file2);
} else {
@stat1 = lstat($file1);
@stat2 = lstat($file2);
my $result = ($stat1[0] == $stat2[0]) && ($stat1[1] == $stat2[1]);
return $result;
=item canonpath($file)
This function returns a cleaned path. It simplifies double //, and remove
/./ and /../ intelligently. For /../ it simplifies the path only if the
previous element is not a symlink. Thus it should only be used on real
sub canonpath($) {
my $path = shift;
$path = File::Spec->canonpath($path);
my ($v, $dirs, $file) = File::Spec->splitpath($path);
my @dirs = File::Spec->splitdir($dirs);
my @new;
foreach my $d (@dirs) {
if ($d eq '..') {
if (scalar(@new) > 0 and $new[-1] ne "..") {
next if $new[-1] eq ""; # Root directory has no parent
my $parent = File::Spec->catpath($v,
File::Spec->catdir(@new), '');
if (not -l $parent) {
pop @new;
} else {
push @new, $d;
} else {
push @new, $d;
} else {
push @new, $d;
return File::Spec->catpath($v, File::Spec->catdir(@new), $file);
=item $newpath = resolve_symlink($symlink)
Return the filename of the file pointed by the symlink. The new name is
canonicalized by canonpath().
sub resolve_symlink($) {
my $symlink = shift;
my $content = readlink($symlink);
return undef unless defined $content;
if (File::Spec->file_name_is_absolute($content)) {
return canonpath($content);
} else {
my ($link_v, $link_d, $link_f) = File::Spec->splitpath($symlink);
my ($cont_v, $cont_d, $cont_f) = File::Spec->splitpath($content);
my $new = File::Spec->catpath($link_v, $link_d . "/" . $cont_d, $cont_f);
return canonpath($new);
=item my $cmdpath = find_command($command)
Return the path of the command if available on an absolute or relative
path or on the $PATH, undef otherwise.
sub find_command($) {
my $cmd = shift;
if ($cmd =~ m{/}) {
return "$cmd" if -x "$cmd";
} else {
foreach my $dir (split(/:/, $ENV{'PATH'})) {
return "$dir/$cmd" if -x "$dir/$cmd";
return undef;
=item my $control_file = get_control_path($pkg, $filetype)
Return the path of the control file of type $filetype for the given
=item my @control_files = get_control_path($pkg)
Return the path of all available control files for the given package.
sub get_control_path($;$) {
my ($pkg, $filetype) = @_;
my $control_file;
my @exec = ("dpkg-query", "--control-path", $pkg);
push @exec, $filetype if defined $filetype;
spawn(exec => \@exec, wait_child => 1, to_string => \$control_file);
if (defined $filetype) {
return undef if $control_file eq "";
return $control_file;
return () if $control_file eq "";
return split(/\n/, $control_file);
=item my $file = find_build_file($basename)
Selects the right variant of the given file: the arch-specific variant
("$basename.$arch") has priority over the OS-specific variant
("$basename.$os") which has priority over the default variant
("$basename"). If none of the files exists, then it returns undef.
=item my @files = find_build_file($basename)
Return the available variants of the given file. Returns an empty
list if none of the files exists.
sub find_build_file($) {
my $base = shift;
my $host_arch = get_host_arch();
my ($abi, $host_os, $cpu) = debarch_to_debtriplet($host_arch);
my @files;
foreach my $f ("$base.$host_arch", "$base.$host_os", "$base") {
push @files, $f if -f $f;
return @files if wantarray;
return $files[0] if scalar @files;
return undef;
=head1 CHANGES
=head2 Version 1.03
New function: find_build_file()
=head2 Version 1.02
New function: get_control_path()
=head2 Version 1.01
New function: find_command()
=head1 AUTHOR
Raphaël Hertzog <>.