This little failing test case illustrates my question: 

# Test error checking for piped system calls
# We use 'boom', a non-existent command, for testing.

use Test::More qw/no_plan/;
use strict;

ok_system_call("true");
ok_system_call("true|true");

not_ok_system_call("boom");
not_ok_system_call("boom|boom");
not_ok_system_call("true|boom");
not_ok_system_call("boom|true");

#################################3

sub ok_system_call {
    my $test = shift;
    my $expect_success = shift;
       $expect_success = 1 if not defined $expect_success;

    my $ok = (system($test) == 0);
    # my $exit_code = $? >> 8;
    # diag "exit code was: $exit_code";

   return $expect_success ? ok($ok, $test) : ok(!$ok, $test);
}

sub not_ok_system_call {
    my $test= shift;
    return ok_system_call($test,0);
}

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The error checking doesn't work correctly on the last one ("boom|true"), so it fails. I believe this happens because although boom fails, something is sent through the pipe, and 'true' succeeds on the other end of the pipe. What's the best practicing for error checking a piped command so this case is covered?

Mark Stosberg

In reply to best practices for checking system return values for piped commands? by markjugg

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