Sed
TODO: Easily available on google
Sed is an extremely handy commandline *nix tool. Refer to its manual page for a more extensive overview of its capabilities.
Uses
Substitution
The most popular command of sed is the s command for substitution. To use the command, type an s, followed by a delimiting character, followed by a regular expression to look for, followed by the delimiting character, followed by an expression with which to replace what was found, followed by a final delimiting character. (/ is the conventional delimiting character and potentially required by some versions of sed. GNU sed can take any character however, and when URLs or paths are involved, % is often a handy choice to lessen the amount of escaping required.)
$ echo "Never let schooling interfere with your education." | sed 's/schooling/video games/' Never let video games interfere with your education.
Groups can be useful in the replacement portion. Use the -r flag if you don't want to escape the initial grouping parenthesis. The -e flag allows for multiple expressions to be evaluated.
$ echo "Never let schooling interfere with your education." | sed -re 's/(schooling)/costly \1/' -e 's/(education)/invaluable \1/' Never let costly schooling interfere with your invaluable education.