edit file with perl command directly

The Following is found on the internet and it seems to be useful. Just put here to be used next time. The source is from the link: http://stackoverflow.com/questions/4388304/in-perl-how-do-i-change-delete-or-insert-a-line-in-a-file-or-append-to-the-b

perl -pi -e 's/Fred/Barney/' inFile.txt

To make a backup of inFile.txt, give -i a file extension to add:

perl -pi.bak -e 's/Fred/Barney/' inFile.txt

To change only the fifth line, you can add a test checking $., the input line number, then only perform the operation when the test passes:

perl -pi -e 's/Fred/Barney/ if $. == 5' inFile.txt

To add lines before a certain line, you can add a line (or lines!) before Perl prints $_:

perl -pi -e 'print "Put before third line\n" if $. == 3' inFile.txt

You can even add a line to the beginning of a file, since the current line prints at the end of the loop:

perl -pi -e 'print "Put before first line\n" if $. == 1' inFile.txt

To insert a line after one already in the file, use the -n switch. It's just like -p except that it doesn't print $_ at the end of the loop, so you have to do that yourself. In this case, print $_ first, then print the line that you want to add.

perl -ni -e 'print; print "Put after fifth line\n" if $. == 5' inFile.txt

To delete lines, only print the ones that you want.

perl -ni -e 'print unless /d/' inFile.txt

… or …

perl -pi -e 'next unless /d/' inFile.txt