Question

I have a list of items in a file,

foobar
barfoo
bar
faaboo
foo
boofar
fo
b

Using perl, I’m just after script that will go through the filename and delete all items 3 characters or less. Overwrite the existing filename (without creating a new, or temp filename), Thus the list will be become.

foobar
barfoo
faaboo
boofar

Answer 1

One-liner:

perl -ine '{print if /.{4}/}' filename

You can use length (add 1 for newline character) instead of regex if that’s your fancy, as Jonathan Leffler noted in comments – it’s probably faster on very large files. Here’s a Windows version (note the use of double quotes required by cmd instead of single quotes):

perl.exe -i.bak -n -e "{print if length > 4}" filename

Also, to answer your comment, unfortunately you can not execute in-place -i edits on Windows without a backup file. Please refer to this SO post for detailed explanation (again, Windows limitation, not Perl’s) as well as a workaround.