trap

Handle shell signals and cleanup

TLDR

List available signal names

$ trap -l

List current trap commands and their signals

$ trap

Execute a command when a signal is received

$ trap 'echo "Caught signal SIGHUP"' SIGHUP

Remove trap commands for signals

$ trap - SIGHUP SIGINT

Ignore a signal

$ trap '' SIGINT

SYNOPSIS

trap [command] [signal...]trap -ltrap -p [signal...]

trap is a shell builtin that executes commands when the shell receives signals. It's commonly used in scripts for cleanup operations (removing temp files), handling interrupts gracefully, and ignoring signals that would otherwise terminate the script.Common signals include SIGINT (Ctrl+C), SIGTERM (termination request), SIGHUP (hangup), EXIT (script exit), and ERR (command error). The EXIT pseudo-signal executes on normal script exit.

PARAMETERS

-l

List signal names and numbers

-p [signal]

Print trap commands for specified signals

command

Command to execute when signal is received

- signal

Reset signal to default behavior

'' signal

Ignore the signal

INSTALL

sudo apk add execline

brew install execline

nix profile install nixpkgs#execline

CAVEATS

Trap is a shell builtin, not an external command. Behavior varies slightly between shells (bash, dash, zsh). Some signals (SIGKILL, SIGSTOP) cannot be trapped. Traps are inherited by subshells but not by external commands.

HISTORY

Originated in the Bourne shell in Unix V7 (1979). The concept of trapping signals comes from the Unix signal handling mechanism. Bash and other modern shells have extended the original functionality with pseudo-signals like ERR and DEBUG.