grep

Matches patterns in input text.
Supports simple patterns and regular expressions.

 - Search for an exact string:
   grep {{search_string}} {{path/to/file}}

 - Search in case-insensitive mode:
   grep -i {{search_string}} {{path/to/file}}

 - Search recursively (ignoring non-text files) in current directory for an exact string:
   grep -RI {{search_string}} .

 - Use extended regular expressions (supporting ?, +, {}, () and |):
   grep -E {{^regex$}} {{path/to/file}}

 - Print 3 lines of [C]ontext around, [B]efore, or [A]fter each match:
   grep -{{C|B|A}} 3 {{search_string}} {{path/to/file}}

 - Print file name with the corresponding line number for each match:
   grep -Hn {{search_string}} {{path/to/file}}

 - Use the standard input instead of a file:
   cat {{path/to/file}} | grep {{search_string}}

 - Invert match for excluding specific strings:
   grep -v {{search_string}}