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grep — Video Man Page

By April 14, 2013One Comment

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

One Comment

  • Clive Darke says:

    -E (a.k.a. egrep) uses Extended Regular Expressions (as defined in POSIX), not “enhanced”.