I just want to share a problem I had this morning using grep -f to obtain the patterns to match from a text file.


$ echo 'sandbox/test/script.py' | grep -G '^sandbox/'

Using -f option fails:

$ echo 'sandbox/test/script.py' | grep -G -f patterns.txt
$ cat patterns.txt

I didn't understand why grep was failing until I inspected the text file:

$ file patterns.txt
/home/miguel/patterns.txt: ASCII text, with CRLF line terminators

This file was being used by different colleagues on different Operating Systems, and someone saved it using the Windows line terminators.

  • 2
    dos2unix will fix it. – Archemar Dec 28 '15 at 15:21
  • Yes, check the solution below. – Miguel Rentes Dec 28 '15 at 15:38
  • -f means fixed patterns, no regexps (and no anchors either). – vonbrand Dec 28 '15 at 16:28
  • That is why I used the -G flag, which interprets a pattern (obtained from the text file) as a basic regular expression. The -f is for obtaining the patterns from a text file, one per line. – Miguel Rentes Dec 28 '15 at 16:34
  • @vonbrand, I think you have -f and -F mixed up – iruvar Dec 28 '15 at 17:23


Using dos2unix solved the problem.

$ dos2unix patterns.txt
dos2unix: converting file /home/miguel/patterns.txt to Unix format ...
$ file patterns.txt
/home/miguel/patterns.txt: ASCII text

And now grep -f works again.

$ echo 'sandbox/test/script.py' | grep -G -f patterns.txt

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