Perl Cookbook

Program: tctee

Not all systems support the classic tee program for splitting output pipes to multiple destinations. This command sends the output from someprog to /tmp/output and to the mail pipe beyond.

% someprog | tee /tmp/output | Mail -s 'check this' [e-mail]

This program helps not only users who aren’t on Unix systems and don’t have a regular tee. It also helps those who are, because it offers features not found on other version of tee.

The four flag arguments are -i to ignore interrupts, -a to append to output files, -u for unbuffered output, and -n to omit copying the output on to standard out.

Because this program uses Perl’s magic open, you can specify pipes as well as files.

% someprog | tctee f1 "|cat -n" f2 ">>f3"

That sends the output from someprog to the files f1 and f2, appends it to f3, sends a copy to the program cat -n, and also produces the stream on standard output.

The program in Example 8.8 is one of many venerable Perl programs written nearly a decade ago that still runs perfectly well. If written from scratch now, we’d probably use strict, warnings, and ten to thirty thousand lines of modules. But if it ain’t broke . . .

Example 8-8. tctee

#!/usr/bin/perl # tctee - clone that groks process tees # perl3 compatible, or better. while ($ARGV[0] =~ /^-(.+)/ && (shift, ($_ = $1), 1)) { next if /^$/; s/i// && (++$ignore_ints, redo); s/a// && (++$append, redo); s/u// && (++$unbuffer, redo); s/n// && (++$nostdout, redo); die "usage $0 [-aiun] [filenames] ...\n"; ...