bwelch has asked for the wisdom of the Perl Monks concerning the following question:

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 ./ 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";
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"; } }
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?