What string set -Eeuo pipefail in shell script does mean?


The string `set -Eeuo pipefail` is a command used in shell scripts, particularly in Bash, to modify the behavior of the script for better error handling and debugging. Here’s what each component means:

  1. `set`: This is a shell builtin command that sets or unsets shell options and positional parameters.
  2. `-E`: This option ensures that the `ERR` trap is inherited by shell functions, command substitutions, and commands executed in a subshell environment. This enhances the error handling capabilities of the script.
  3. `-e`: The `-e` option causes the script to exit immediately if any command it runs exits with a non-zero status (i.e., it encounters an error). This prevents errors from snowballing and makes it easier to pinpoint where a script is failing.
  4. `-u`: This option treats unset variables and parameters other than the special parameters “@” and “*” as an error when performing parameter expansion. If you try to use a variable that hasn’t been set, the script will exit, which helps catch typos and other mistakes.
  5. `-o pipefail`: The `-o` option sets various shell attributes. `pipefail` is an option that affects pipelines, which are sequences of commands connected by pipes (`|`). With `pipefail` enabled, the return value of a pipeline is the status of the last command to exit with a non-zero status, or zero if no command exited with a non-zero status. This makes it easier to detect failures in any part of a pipeline and is particularly useful for debugging and ensuring correct script behavior.

In summary, `set -Eeuo pipefail` is a common set of options used in shell scripts to make them more robust and less prone to common errors. It’s especially useful in scripts where correct error handling and script behavior are critical.