For example, in some tools, you might search "id=([0-9])+" then in the replacement string you could use \1 to refer to whatever number matched the expression in the parentheses.

Regular expressions are by far the most powerful tool for text manipulation and description, and they are well supported under Linux on many applications. Unfortunately, they are not supported at all ...

Regular expressions — the things you feed to programs like grep — are a bit like riding a bike. It seems impossible until you learn to do it, and then it’s easy. Part of their bad… ...

When working with regular expressions in a shell script the norm is to use grep or sed or some other external command/program. Since version 3 of bash (released in 2004) there is another option: ...