Re: Need help understanding code snippet with "grep -f"

[Anonymous Monk]

My guess what this does is:

Don't guess, read the docs, grep is not like grep, grep is like foreach that filters out wanted list items

[fifaltra]

Well, I did read it, but I couldn't figure out what the -f does there, and how the behaviour of grep described in the docs would give me a list of existing files. But that's probably cleared up now. Is there also documentation on this "-f" thing? Because it's really hard to google for something as short as "-f"...

[Anonymous Monk]

See -X.

[Anonymous Monk]

Is there also documentation on this "-f" thing? Because it's really hard to google for something as short as "-f"...

yup, it can be, but here is a tip, if you use perldoc://"-f" in perlmonks search box its like "-f" site:perldoc.perl.org -> http://perldoc.perl.org/functions/-X.html

[GotToBTru]

Reading this reminded me .. I had the exact same thing trip me up. -f is not a switch to the grep function but rather an independently defined function that just happens to be used as an argument here. But the unix-familiar mind sees that and thinks "grep -f" is a special form of "grep" and seeks the answer in the grep documentation. And doesn't find it.

Using the block form of grep might have made this clearer.

@files = grep { -f } glob("~/data/*");