protect-scripts-by-using-set-flags

Protect scripts by using set flags

For POSIX scripts, please start with:

set -euf

For bash/zsh scripts, please start with:

set -euf -o pipefail

Meanings:

• set -e or set -o errexit: if there is an error, then exit immediately.

• set -u or set -o nounset: disallow unset variables.

• set -f or set -o noglob: diasble filename globbing.

• set -o pipefail: if a pipe fails, then exit immediately and use the pipe's exit status.

Note: some scripts won't be able use all these flags. For example, a script that needs filename globbing cannot use set -f because it disables globbing. Please note this in the code immediately above the set line.

For Bash help on the set command see: https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

Advice

Some programmers debate the usefulness of these flags, because they cause immediate exits, which isn't always what the programmer expects or wants.

A more-sophisticated approach is write proper error handing for each function.