set

Enable strict mode (exit on error, undefined variables, pipeline failures)

$ set -euo pipefail

$ set -e

$ set -u

$ set -x

$ set +x

$ set -f

$ set

$ set -- [arg1] [arg2] [arg3]

set [-abefhkmnptuvxBCEHPT] [-o option-name] [--] [arg...]

set is a shell builtin that controls shell options and positional parameters. Options modify shell behavior for scripting, debugging, and interactive use. Use - to enable an option and + to disable it.
When invoked without arguments, set displays all shell variables and functions. With -- followed by arguments, it sets the positional parameters ($1, $2, etc.) to the provided values.
The combination set -euo pipefail is a common "strict mode" for shell scripts that causes immediate exit on errors, undefined variable references, or pipeline failures—catching bugs early and preventing silent failures.

-a (allexport)

Export all created or modified variables and functions

Report terminated background job status immediately

Exit immediately if a command returns non-zero status

Disable filename expansion (globbing)

Remember command locations as they are looked up

Place all assignment arguments in the environment

Enable job control

Read commands but do not execute them (syntax check)

Enable privileged mode

Exit after reading and executing one command

Treat unset variables as an error during expansion

Print shell input lines as they are read

Print commands and arguments before execution

Enable brace expansion (default on)

Prevent overwriting files with output redirection

ERR trap is inherited by shell functions and subshells

Enable ! style history substitution

Do not resolve symbolic links for commands like cd

DEBUG and RETURN traps inherited by functions

Pipeline returns status of last non-zero command

End of options; remaining args become positional parameters

The -e option has many exceptions: it does not trigger exit for commands in if tests, while/until conditions, commands negated with !, or the left side of && and ||. Understanding these exceptions is important for reliable error handling in scripts.

The set command has been part of the Bourne shell since its creation by Stephen Bourne at Bell Labs in 1979. It was included in POSIX and extended in bash with additional options like pipefail. The concept of shell options predates even the Bourne shell, with roots in early Unix shells.

bash(1), sh(1), shopt(1), unset(1), export(1)