PERL Miscellaneous - Getting stderr when using '-|'

Author

Getting stderr when using '-|'

bill

2004-12-30, 3:57 am

I want to use exec($prog, @args) to execute a system command without
worrying about shell escapes, but I also want to capture both stdout
and stderr from this system command. If I only wanted stdout, I
could do something like this

die "Can't fork: $!" unless defined(my $pid = open(my $read_child, '-|'));

if ($pid == 0) {
exec($prog, @argv) or die "Can't exec $prog: $!\n";
exit 0; # superfluous
}

my $output = do { local $/ = undef;, <$read_child> };
close $read_child;
if ($?) {
die "Child failed: $?"
}

In the code above, $output captures the stdout from the command
run through exec. But how does one capture stderr as well? Not
surprisingly adding the string '2>&1' to exec's arguments fails
because exec just passes this string along as one more argument to
$prog.

Any help would be much appreciated.

bill

KKramsch

2004-12-30, 3:57 am

In <cr0539$so4$1@reader1.panix.com> bill <please_post@nomail.edu> writes:

>I want to use exec($prog, @args) to execute a system command without
>worrying about shell escapes, but I also want to capture both stdout
>and stderr from this system command. If I only wanted stdout, I
>could do something like this

>die "Can't fork: $!" unless defined(my $pid = open(my $read_child, '-|'));

>if ($pid == 0) {

open (STDERR, '>&STDOUT') or die "Can't dup STDOUT\n";

> exec($prog, @argv) or die "Can't exec $prog: $!\n";
> exit 0; # superfluous
>}

>my $output = do { local $/ = undef;, <$read_child> };
>close $read_child;
>if ($?) {
> die "Child failed: $?"
>}

HTH,

Karl

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Paul Lalli

2004-12-30, 8:57 am

"bill" <please_post@nomail.edu> wrote in message
news:cr0539$so4$1@reader1.panix.com...
>
> I want to use exec($prog, @args) to execute a system command without
> worrying about shell escapes, but I also want to capture both stdout
> and stderr from this system command.

Have you read the appropriate FAQ on this topic?
perldoc -q stderr

Paul Lalli

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