pipe output to perl

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

Replies are listed 'Best First'.
Re: pipe output to perl by ikegami (Patriarch) on Dec 04, 2008 at 12:11 UTC
The prints aren't in a loop, so why would it print before/after every line? `perl -e 'while (<>) { print "XXX\n" ;print; print "XXX" }'` [download] Or use -n `perl -ne 'print "XXX\n" ;print; print "XXX"'` [download] Or even -p `perl -pe '$_ = "XXX\n" . $_ . "XXX"'` [download] Then there's the useless use of `cat`. `cat filename` is a waste of resource. Use "`<`" instead. `perl -e'...' < /tmp/file` [download] Or since `<>` (including -n and -p) treats the arguments as files to read, just `perl -e'...' /tmp/file` [download] All together: `perl -pe '$_ = "XXX\n" . $_ . "XXX"' /tmp/file` [download]	[reply] [d/l] [select]
Re: pipe output to perl by Corion (Patriarch) on Dec 04, 2008 at 11:55 UTC
See perlrun, especially about the `-p` and `-n` switches. Your code does not contain any loop and hence Perl will only print XXX two times.	[reply] [d/l] [select]
Re: pipe output to perl by poolpi (Hermit) on Dec 04, 2008 at 15:36 UTC
At the end... `perl -pe 'END{print "XXX"} s/^/XXX\n/' file perl -ple 'END{print "XXX"} print "XXX"' file perl -lane 'END{print "XXX"} print "XXX\n$F[0]"' file` [download] hth, PooLpi 'Ebry haffa hoe hab im tik a bush'. Jamaican proverb	[reply] [d/l]