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content/blog/bash-traps-exit-error-sigint.md

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+---
+title: "Bash Traps: Exit, Error, Sigint"
+date: 2024-01-02T11:26:06-05:00
+draft: false
+tags: []
+math: false
+medium_enabled: false
+---
+
+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.
+
+## `SIGINT`
+
+If we have a while loop within a bash script
+
+```bash
+while sleep 0.1; do
+  do_something
+done
+```
+
+We probably want to be able to CTRL-C to exit the whole script.
+
+```bash
+finish () {
+  exit 0
+}
+trap finish SIGINT
+
+while sleep 0.1; do
+  do_something
+done
+```
+
+## `ERR`
+
+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.
+
+```bash
+set -o errexit
+set -o nounset
+set -o pipefail
+
+print_debug () {
+  declare exit_code=$?
+  env >&2
+  other_debug_info >&2
+  exit "$exit_code"
+}
+
+trap print_debug ERR
+
+command_that_may_fail
+```
+
+## `EXIT`
+
+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.
+
+This is useful for cleaning up build files, de-provisioning services, etc.
+
+```bash
+cleanup () {
+  rm a.tmp b.tmp
+  deprovision
+}
+
+trap cleanup EXIT
+
+long_compile_may_fail
+```
+
+## Other Resources
+
+http://redsymbol.net/articles/bash-exit-traps/
+
+https://jakski.github.io/pages/error-handling-in-bash.html