Perl One-Liners

Chapter 7. Selectively Printing and Deleting Lines

In this chapter, we’ll examine various one-liners that print and delete certain lines. These one-liners will, for example, print repeated lines, print the shortest line in a file, and print lines that match certain patterns.

But every one-liner that prints certain lines can also be viewed as one that deletes the lines that aren’t printed. For example, a one-liner that prints all unique lines deletes all repeated lines. I’ll discuss only the one-liners that print something, rather than delete something, because one is always the inverse of the other.

7.1 Print the first line of a file (emulate head -1)

perl -ne 'print; exit' file

This one-liner is quite simple. Perl reads the first line into the