- trap - trap signals and conditions
- trap [ options ] [action condition ...]
- trap is a special built-in that defines actions to be taken when conditions such as receiving a signal occur. Also, trap can be
used to display the current trap settings on standard output.
- If action is -, trap resets each condition to the default value. If action is an empty string, the shell
ignores each of the conditions if they arise. Otherwise, the argument action will be read and executed by the shell as if it were
processed by eval(1) when one of the corresponding conditions arise. The action of the trap
will override any previous action associated with each specified condition. The value of $? is not altered by the trap execution.
- condition can be the name or number of a signal, or one of the following:
- This trap is executed when the shell exits. If defined within a function defined with the function
reserved word, the trap is executed in the caller's environment when the function returns and the trap action is restored to the value it had when
it called the function.
- Same as EXIT.
- Executed before each simple command is executed but after the arguments are expanded.
- Executed whenever set -e would cause the shell to exit.
- Executed when a key is entered from a terminal device.
- Signal names are case insensitive and the sig prefix is optional. Signals that were ignored on entry to a noninteractive shell cannot
trapped or reset although doing so will not report an error. The use of signal numbers other than 1, 2, 3, 6, 9,
14, and 15 is not portable.
- Although trap is a special built-in, specifying a condition that the shell does not know about causes trap to exit with a
non-zero exit status, but does not terminate the invoking shell.
- If no action or conditions are specified then all the current trap settings are written to standard output.
- Causes the current traps to be output in a format that can be processed as input to the shell to recreate the current traps.
- Successful completion.
- An error occurred.
- kill(1), eval(1), signal(3)
- trap (AT&T Research) 1999-07-17
- David Korn <email@example.com>
- Copyright © 1982-2010 AT&T Intellectual Property