The Perl Toolchain Summit 2025 Needs You: You can help 🙏 Learn more

=head1 NAME
Panotools::Makefile::Utils - Makefile syntax
=head1 SYNOPSIS
Simple interface for generating Makefile syntax
=head1 DESCRIPTION
Writing Makefiles directly from perl scripts with print and "\t" etc... is
prone to error, this library provides a simple perl interface for assembling
Makefile rules.
See L<Panotools::Makefile::Rule> and L<Panotools::Makefile::Variable> for
object classes that you can use to contruct makefiles.
=cut
use strict;
use vars qw /@ISA @EXPORT_OK/;
@ISA = qw /Exporter/;
@EXPORT_OK = qw /platform quotetarget quoteprerequisite quoteshell/;
our $PLATFORM;
=head1 USAGE
Access the current platform name (MSWin32, linux, etc...):
print platform;
Define a different platform and access the new name:
platform ('MSWin32');
print platform;
Reset platform to default:
platform (undef);
=cut
sub platform
{
$PLATFORM = shift if @_;
return $PLATFORM if defined $PLATFORM;
return $^O;
}
=pod
Take a text string (typically a single filename or path) and quote/escape
spaces and special characters to make it suitable for use as a Makefile
'target' or 'prerequisite':
$escaped_target = quotetarget ('My Filename.txt');
$escaped_prerequisite = quoteprerequisite ('My Filename.txt');
Note that the =;:% characters are not usable as filenames, they may be used as
control characters in a target or prerequisite. An exception is the : in
Windows paths such as C:\WINDOWS which is understood by gnu make.
* and ? are wildcards and will be expanded. You may find that it is
possible to use these as actual characters in filenames, but this assumption
will lead to subtle errors.
$ can be used in a filename, but when used with brackets, ${FOO} or $(BAR),
will be substituted as a make variable.
Targets starting with . are special make targets and not usable as filenames,
the workaround is to supply a full path instead of a relative path. i.e:
/foo/bar/.hugin rather than .hugin
Additionally the ?<>*|"^\ characters are not portable across filesystems (e.g.
USB sticks, CDs, Windows) and should be avoided in filenames.
=cut
sub quotetarget
{
my $string = shift;
# Transform all C:\foo\bar paths to C:/foo/bar
$string =~ s/\\/\//g if (platform =~ /^(MSWin|dos)/);
$string =~ s/([ #|\\])/\\$1/g;
# escape $ as $$ unless part of a $(VARIABLE)
$string =~ s/\$([^({]|$)/\$\$$1/g;
return $string;
}
sub quoteprerequisite
{
my $string = shift;
# Transform all C:\foo\bar paths to C:/foo/bar
$string =~ s/\\/\//g if (platform =~ /^(MSWin|dos)/);
$string =~ s/([ #|\\])/\\$1/g;
# escape $ as $$ unless part of a $(VARIABLE)
$string =~ s/\$([^({]|$)/\$\$$1/g;
return $string;
}
=pod
Take a text string, typically a command-line token, and quote/escape spaces and
special characters to make it suitable for use in a Makefile command:
$escaped_token = quoteshell ('Hello World');
=cut
sub quoteshell
{
my $string = shift;
if (platform =~ /^(MSWin|dos)/)
{
# Transform all C:\foo\bar paths to C:/foo/bar
# Not all tokens are file paths, so \:-) will become /:-)
$string =~ s/\\/\//g;
# hash is parsed by make as a comment, backslash escape
$string =~ s/#/\\#/g;
# caret escape " since we are using it for quoting
$string =~ s/"/^"/g;
# escape $ as $$ unless part of a $(VARIABLE)
$string =~ s/\$([^({]|$)/\$\$$1/g;
# ?<>:*|"^ are unusable in Windows filenames,
# other unix shell characters are unspecial in Windows
# so the only thing we can quote is a space, ampersand, caret and single quote
$string = '"'.$string.'"' if $string =~ /[ &^']/;
}
else
{
# some shell char sequences are useful shell commands
# others are automatic variables $(<D) $(<F) $<
unless ($string =~ /^([&<>|]|>>|2>>|2>|\|\||&&|2>&1|`[^`]+`)$/
or $string =~ /^(\$\(<D\)|\$\(<F\)|\$<|\$@|\$%|\$\?|\$\^|\$\+|\$\||\$\*)$/)
{
# backslash escape shell characters
$string =~ s/([!#'"() `&<>|\\])/\\$1/g;
# unquote $(FOO) variables escaped above
$string =~ s/\$\\\(([^)]+)\\\)/\$($1)/g;
# double escape $ as \$$ unless part of a $(VARIABLE)
$string =~ s/\$([^({]|$)/\\\$\$$1/g;
}
}
return $string;
}
1;