How to shuffle lines using the command line

Sorting lines is easy: everybody knows the sort command.

But what if you want to do the other way around,
and shuffle instead of sorting?

This perl one-liner does just that:

... | perl -MList::Util -e 'print List::Util::shuffle <>'

Explanation:

• -MList::Util load the List::Util module (as if doing use List::Util inside a Perl script)
• -e '...' execute Perl command
• print List::Util::shuffle <> call List::Util::shuffle for the lines coming from standard input, read by <>

Another way would be sort -R if your version of sort supports that (GNU, as opposed to BSD).
In BSD systems you can install coreutils and try gsort -R instead.
(For eample on OSX, using MacPorts: sudo port install coreutils.)

Yet another way is shuf in GNU systems,
and gshuf in coreutils.