Question

I have a Perl script using a system call to sort a tsv file:

system("sort -k8 -r -n -t \$'\t' in.txt > out.txt");

It works fine in CentOS and SUSE Linux. But in Ubuntu, it gives an error:

sort: multi-character tab `$\t'

It seems the problem with different OS interpret the quote differently. Do you have a simple but more robust method to sort a tsv file in Perl?

Answer 1

Usually, you’d use an array invocation of system to avoid the shell, but you have I/O redirection in the command, which is fiddly to deal with. OTOH, sort allows you to specify the output file with -o, and the named file could be one of the inputs (though it won’t be here):

my @cmd = ( "sort", "-k8", "-rn", "-t", "\t", "-o", "out.txt", "in.txt" );

system(@cmd);

The shell is not invoked; the tab is not mangled. I combined the -r and -n options into one; you could leave them separate if you prefer, or (at a pinch) add them after the -k8 option.