set

What it does

How to write it

set [-abefhkmnptuvxBCEHPT] [-o OPTION] [--] [ARGUMENT]...

Most used

Nothing matches this filter.

$ run as a normal user# run as root (or with sudo)

1. 1Strict mode for scripts

   $head -2 /usr/local/bin/backup.sh
   #!/bin/bash
   set -euo pipefail

   Many hidden errors become visible.

2. 2Trace part of a script

   $set -x; cp a b; set +x
   + cp a b

   Only these lines are traced.

3. 3Stop on errors

   $bash -c 'set -e; false; echo "not reached"'

   The script ends at false.

4. 4Unset variable error

   $bash -c 'set -u; echo "$TYPO"'
   bash: line 1: TYPO: unbound variable

   Catches typos like rm -rf "$DIR/" with an empty DIR.

5. 5Pipe failures

   $bash -c 'set -o pipefail; false | true; echo $?'
   1

   Without pipefail the result would be 0.

6. 6Do not overwrite files

   $set -C; echo x > existing.txt
   bash: existing.txt: cannot overwrite existing file

   Protects against a wrong >.

7. 7vi mode on the command line

   $set -o vi

   Esc, then vi keys to edit.

8. 8Show all options

   $set -o | head

   on/off for each.

9. 9Set positional parameters

   $set -- one two three; echo "$2 / $#"
   two / 3

   Useful in tests and functions.

10. 10List variables and functions

    $set | grep ^HIST

    All HIST variables.

Nothing matches this filter.

Exit codes