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Using perl 5.8.0 on Solaris, I sometimes use system calls to manipulate a file or directory. This has worked well in the past, but this week a script failed trying to copy a file. The error message was "Illegal seek at ./script.pl line XXX", and the system call causing the error is here:

use strict;
system( "cp /analysis/fasta1.fa /analysis2/fasta1.fa" ) 
    or die print "Can't copy fasta file: $! \n";
[download]

A friend at work said that in his experience, the return code from "system" isn't reliable when used that way. He said I should capture the actual return code from the system call and evaluate it. If it's not zero, there's an error and to print $! at that point. I followed his recommendation and the problem went away. Here's the code I used.

use strict;
&doSystemCommand(  "cp /analysis/fasta1.fa /analysis2/fasta1.fa"  );

sub doSystemCommand
{
    my $systemCommand = $_[0];

    print LOG "$0: Executing [$systemCommand] \n";
    my $returnCode = system( $systemCommand );

    if ( $returnCode != 0 ) 
    { 
        die "Failed executing [$systemCommand]\n"; 
    }
}
[download]

Could you tell me more about what is happening here and why this eliminated the errors? Also, could you offer improvements in this function for handling system calls?

In reply to Best method to capture return code from system calls? by bwelch

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