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grep — Video Man Page

By April 14, 2013September 12th, 2022No Comments

The Linux command line tool grep is your first step in learning regular expressions, or at least allowing you practice. It is a powerful tool that is as easy as -A -B and -C to use; we will see the switches later that put context to our searches and are often overlooked.

First we confirm that the use of fgrep and egrep in depreciated with grep containing:

  • -E for enhanced regex
  • -F for fast grep

Moving onto to the -i option to ignore case and the really useful -w to enable complete word search that saves us building word boundaries into the regex. If we need to reverse the search we can use -v for invert, however we also have the option -L that is useful when search multiple files to show those that don’t match as well as -l to show matching files.

We end up with the context switches

  • -A3 show 3 lines after the match
  • -B3 show three lines before
  • -C3 show 3 lines before and after