Hi Peter,
On 2 Mar 2012 02:48:28 -0000
Peter Scott <pe...@psdt.com> wrote:
> On Sun, 26 Feb 2012 20:30:56 +0100, Manfred Lotz wrote:
> > I want to run a shell command with the following constraints:
> >
> > a. I like to get the return code of the command b. Furthermore I want to
> > combine stdout and stderr so that the output comes in a natural sequence
> > like in the shell. c. I don't want to capture the output in a variable
> > (because the output could be really large and I don't want to wait for
> > the first line of output)
> >
> > I did this:
> >
> > use IPC::Open3;
> >
> > sub run_cmd {
> > my $cmd = shift @_;
> >
> > my $pid = open3(undef, *CMD_OUT, *CMD_OUT,$cmd);
> >
> > while ( <CMD_OUT>) { print "$_"; }
> > waitpid($pid,0);
> > my $rc = $? >>8;
> > return $rc;
> > }
> >
> >
> > I tested the code and it I can say it worked fine under fair weather
> > conditions.
> >
> > Question: Is the code ok, or could it be improved, or has it even flaws?
>
> It doesn't have flaws. You could do it without the module with a piped
> open:
>
> sub run_cmd
> {
> my $cmd = shift;
>
> open my $fh, '-|', "$cmd 2>&1" or die "open: $!";
> print while <$fh>;
> close $fh;
> return $? >> 8;
> }
Interesting. I did not realise that open '-|' with a single argument will pass
this as a small shell program. But it does:
<<<<
#!/usr/bin/perl
use strict;
use warnings;
sub run_cmd
{
my $cmd = shift;
open my $fh, '-|', "$cmd 2>&1" or die "open: $!";
print while <$fh>;
close $fh;
return $? >> 8;
}
run_cmd('ls -l');
>>>>
This may cause security problems if you pass an array («open my $fh, '-|',
@cmd or die …») because if it contains only one element, then you're risking
code/markup injection. And open does not appear to support system()'s or
exec()'s «system { $args[0] } @args» paradigm.
When I asked people on #p5p (the Perl 5 Porters channel) about it, they told
me that open sucks for that and that one should use
https://metacpan.org/release/IPC-Run or
https://metacpan.org/release/IPC-System-Simple
(depending on what you want to do) instead.
Regards,
Shlomi Fish
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