[dozzie]

I would also recommend to read Single Unix Specification on shell syntax, and then avoid bashisms whenever possible. Bash had a history of subtly changing its behaviour in these, which leads to scripts getting suddenly broken without any modification on system update.

[zanchey]

Could you give some examples? http://wiki.bash-hackers.org/scripting/bashchanges and http://wiki.bash-hackers.org/scripting/obsolete aren't particularly enlightening.

[dozzie]

What I was hit with were subtle changes to how [[ ]] worked, along the lines of implicit anchoring in pattern in previous version not taking place in succeeding version. It took quite a while to debug what became a logic error.

After that I started avoiding bashisms in my scripts, especially that they usually provide very little benefit at the cost of gambling against breaking silently on a barely related update.

Nowadays it's also worth noting that #!/bin/sh often (Debian derivatives) points to something that is not Bash, and people writing in shell/Bash usually don't understand the difference.