PerlOneLiners

One-liners we keep looking up. Add yours.

# in-place edit with backup
perl -pi.bak -e 's/foo/bar/g' *.conf

# print lines 10 to 20
perl -ne 'print if 10..20' file

# sum a column
perl -lane '$s += $F[2]; END { print $s }' data.txt

# remove duplicate lines, keep order
perl -ne 'print unless $seen{$_}++' file

# convert DOS line endings
perl -pi -e 's/\r\n/\n/' file.txt

# print the longest line
perl -ne '$l = $_ if length > length $l; END { print $l }' file

# count occurrences of each word
perl -lne 'for (split) { $c{lc $_}++ } END { print "$c{$_}\t$_" for sort { $c{$b} <=> $c{$a} } keys %c }' file

# random line
perl -e 'srand; rand($.) < 1 && ($line = $_) while <>; print $line' file

# extract email addresses
perl -wne 'while (/[\w.+-]+@[\w-]+\.[\w.-]+/g) { print "$&\n" }' *.txt

Notes:

• -l chomps input and adds newline to print. -a autosplits into @F. -n wraps in while(<>). -p same but prints $_ at the end.
• -i without a suffix means no backup. You will regret that once.
• On Solaris the perl in /usr/bin is 5.005. Use /usr/local/bin/perl. -- Thomas

See also the Camel book chapter 19, and perldoc perlrun.