UNIX for Dummies Questions & Answers

Hi all,

I know the one liner to delete all the lines in a file which matches a pattern
i.e

perl -i.old -ne 'print unless /pattern/' file

Now i need the perl onliner to delete all the lines which doesnt match the pattern. Also what is the difference between perl -i and perl -i.old.
Does perl -i.old archive the existing file?

Your help in this will be appreciated.

Thanks in advance.

Lijju

Only print lines matching the pattern:

Code:

perl -i.old -ne 'print if /pattern/' file

-i tells perl to modify a file in-place, -i.old or -i.bak or whatever you like, tells perl to make a backup first using the specified extension. See 'man perlrun' for the specifics.