BASH’s compat31 option

Several of my bash scripts failed when I migrated from Debian to Gentoo almost one year ago for the different ways bash interpretes commands like this: [[ "$x" =~ '^[0-9]$' ]]. This command succeeded in Debian when $x is a single digit, but failed in Gentoo. I had to remove the single quotes surround the regular expression to make it work in Gentoo.

Today I finally found the reason: I was using bash 3.1 in Debian and 3.2 in Gentoo. Bash 3.2 by default mandates that regular expressions not be surrounded by quotes; however, the behavior can be modified using shopt -s compat31.

---

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.

Related posts:

1. Extended pattern matching in BASH
2. How BASH Changes Terminal Window Title
3. globstar in bash 4 follows directory symlinks
4. Extract Deb files from command line

Tags: bash