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content/blog/bash-traps-exit-error-sigint.md
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content/blog/bash-traps-exit-error-sigint.md
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---
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title: "Bash Traps: Exit, Error, Sigint"
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date: 2024-01-02T11:26:06-05:00
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draft: false
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tags: []
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math: false
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medium_enabled: false
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---
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Traps in bash listen for interrupts and signals and performs a bash command in response to it. This post will go over three use cases I've encountered so far in my bash scripting journey.
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## `SIGINT`
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If we have a while loop within a bash script
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```bash
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while sleep 0.1; do
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do_something
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done
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```
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We probably want to be able to CTRL-C to exit the whole script.
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```bash
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finish () {
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exit 0
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}
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trap finish SIGINT
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while sleep 0.1; do
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do_something
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done
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```
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## `ERR`
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If we encounter an error in a bash script, one thing we might want to do is dump the environment information and other things that can be useful for debugging.
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```bash
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set -o errexit
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set -o nounset
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set -o pipefail
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print_debug () {
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declare exit_code=$?
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env >&2
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other_debug_info >&2
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exit "$exit_code"
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}
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trap print_debug ERR
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command_that_may_fail
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```
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## `EXIT`
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Like the last one, this function will occur if the script fails. However, this also occurs if the script is successful. It's similar to the `finally` clause within a `try-catch` programming paradigm.
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This is useful for cleaning up build files, de-provisioning services, etc.
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```bash
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cleanup () {
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rm a.tmp b.tmp
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deprovision
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}
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trap cleanup EXIT
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long_compile_may_fail
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```
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## Other Resources
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http://redsymbol.net/articles/bash-exit-traps/
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https://jakski.github.io/pages/error-handling-in-bash.html
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