FAQ 8.28 How can I call backticks without shell processing?

This is an excerpt from the latest version perlfaq8.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

------------------------------------------------------------ --------

8.28: How can I call backticks without shell processing?

This is a bit tricky. You can't simply write the command like this:

@ok = `grep @opts '$search_string' @filenames`;

As of Perl 5.8.0, you can use "open()" with multiple arguments. Just
like the list forms of "system()" and "exec()", no shell escapes happen.

open( GREP, "-|", 'grep', @opts, $search_string, @filenames );
chomp(@ok = );
close GREP;

You can also:

my @ok = ();
if (open(GREP, "-|")) {
while () {
chomp;
push(@ok, $_);
}
close GREP;
} else {
exec 'grep', @opts, $search_string, @filenames;
}

Just as with "system()", no shell escapes happen when you "exec()" a
list. Further examples of this can be found in "Safe Pipe Opens" in
perlipc.

Note that if you're using Windows, no solution to this vexing issue is
even possible. Even if Perl were to emulate "fork()", you'd still be
stuck, because Windows does not have an argc/argv-style API.



------------------------------------------------------------ --------

The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.