Many programs use regular expression to find & replace text. However, they tend to come with their own different flavor.

You can probably expect most modern software and programming languages to be using some variation of the Perl flavor, "PCRE"; however command-line tools (grep, less, ...) will often use the POSIX flavor (sometimes with an extended variant, e.g. egrep or sed -r). ViM also comes with its own syntax (a superset of what Vi accepts).

This cheatsheet lists the respective syntax of each flavor, and the software that uses it.

GNU Readline is the library used to make advanced command-line wizardry convenient and consistent across a multitude of command-line applications. These programs include bash, bc, ftp, gnuplot, gpg, ksh, mysql, psql, python, smbclient, xmllint and zsh.

The cheatsheet at the right contains a summary of many of the useful line editing command shortcuts which are available in all applications that use libreadline.