Perl One-Liners

Chapter 2. Spacing

In this chapter, we look at various one-liners that change line and word spacing, performing such tasks as double- and triple-spacing lines in a file, removing blank lines, and double-spacing words. You’ll also learn about various command-line arguments, such as -p, -e, -n, and special variables, such as $_ and $\.

2.1 Double-space a file

perl -pe '$\ = "\n"' file

This one-liner double-spaces a file. I need to explain three things here: the -p and -e command-line options and the short $\ = "\n" Perl program.

Use the -e option to enter a Perl program directly at the command line. Typically you won’t want to create source files for every small program; with -e you can easily write a program directly at the command line as a one-liner. ...