Hi Ken,

Just to pick up on what the AM mentioned: properly closeing a piped open is important so one can catch all possible errors (as opposed to closeing regular files, where in my experience things go wrong much less often). I see you used autodie, but as far as I can tell it doesn't catch errors when the filehandle is implicitly closed when it goes out of scope.

In your code, if I replace the command with something that returns a nonzero exit code, and add the close at the end of the sub, I get confusing results: inside of capture, the error doesn't seem to get caught at all, and outside of capture, I get the confusing error message "Can't close(GLOB(0x8e2b62)) filehandle: '' at ...". (In fact, if I remember correctly, strange interactions with autodie and piped opens is one of the reasons I started avoiding autodie.)

So here's the same run_external_command code, without autodie but with the minimum error handling:

my $extcmd = 'cat';
open my $cmd_pipe, '|-', $extcmd or die "open $extcmd: $!";
print $cmd_pipe "password\n";
close $cmd_pipe or die "close $extcmd: ".($! ? $! : "\$?=$?");

[download]

However, nowadays I very much prefer to use more better-suited modules, one of my favorites is IPC::Run3. For the OP:

use IPC::Run3 'run3';
my $stdin = "password\n";
my @extcmd = ('cat');
run3 \@extcmd, \$stdin, \my $stdout, \my $stderr
    or die "run3 failed";
$? and die "run3: \$?=$?";
print "stdout: <<$stdout>>\n";
print "stderr: <<$stderr>>\n";

[download]

Regards,
-- Hauke D

In reply to Re^2: How to pass data as STDIN to Capture::Tiny by haukex
in thread How to pass data as STDIN to Capture::Tiny by Anonymous Monk

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