Two simple tricks for better shell script error handling

I haven't run into any problems (yet) obstructing signal propagation in my scripts but as you point out it's not The Correct Thing To Do. For the sake of correctness I'll be updating my error handling code. I find doing the correct thing often saves me from debugging strange edge cases.

(replied to on blog comments as well)

Usually when when the Ubuntu `sh -> dash' link is pointed out, it is meant as a warning to use the proper sha-bang, instead of just using `#!/bin/sh'.

If you're arguing that classic shell scripting doesn't carry you all that far, I would agree, but I don't see the harm in using #!/bin/bash or #!/bin/ksh in lieu of sh the few times you are writing a shell script; they are both extremely common and feature many conveniences.

I used to have quite an amount of Korn shell scripts, but of course that was on commercial Unices (with some ksh-retro-fitted Linux boxes in the mix).

Having ksh93 available on all systems was pretty nice, and there definitely was a place for some of the features without going for something else (which in this case mostly was Perl).

I find using specific shebangs is a good habit if you don't know exactly which generic POSIX shell features/syntax you can rely on. In years past I would all too often use #!/bin/sh for the shebang only to find out later I had accidentally used a BASH specific shell feature, which is fine if /bin/sh happens to point to /bin/bash but can break if it points to something else.

OTOH, I believe the error handling tricks discussed should work with any POSIX shell so I've updated the shebang line in the code snippets to use the more generic #!/bin/sh.