[tryauuum]

shorter version of the grep command is

    grep -oP 'prefix \K\d+(?= suffix)'

but yeah, I know it's easier to me because I did read man page at some point (while carefully avoiding perl manuals)

actually even that is not true, perldoc on regular expressions really helps even grep users

[jraph]

In all honesty, I'm more likely to remember this form than the Perl one, and once it's in the shell history, any will do anyway :-)