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Debugging Bash Like a Sire (2023)

Many engineers have a strained relationship with Bash. I love it though, but I’m very aware of it’s limitations when it comes to error handling and data structures (or lack thereof). As a result of these limitations I often see Bash scripts written very defensively that define something like: set -euxo pipefail These are bash builtin options that do more or less sensible things. e: Exit immediately when a non-zero exit status is encountered u: Undefined variables throws an error and exits the script x: Print every evaluation. o pipefail: Here we make sure that any error in a pipe of commands will fail the entire pipe instead just carrying on to the next command in the pipe. All of these are quite useful, thought I tend to skip the -u flag as bash scripts often interact with global variables that are set outside my scripts. The -x flag is extremely noisy so it’s most often used manually when debugging. And to be honest, I don’t really use -o pipefail either. I guess this is a good place for a few words of caution when it comes to this approach. Feel free to dig into this reddit comment, but to summarize, the behavior of these flags aren’t consistent across Bash versions and they can break your scripts in unexpected ways.

Feel free to dig into this reddit comment, but to summarize, the behavior of these flags aren’t consistent across Bash versions and they can break your scripts in unexpected ways. Then we print a neatly formatted string of the data we’ve gathered and prepend>&2 which redirects the output to stderr instead of stdout. This way, if the script suddenly exits due to any non-zero result, we still get an error logged and a stack trace, like a Sire.

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