Trap signals and other events.
Defines and activates handlers to be run when the shell receives signals
or other conditions.
ARG is a command to be read and executed when the shell receives the
signal(s) SIGNAL_SPEC. If ARG is absent (and a single SIGNAL_SPEC
is supplied) or `-', each specified signal is reset to its original
value. If ARG is the null string each SIGNAL_SPEC is ignored by the
shell and by the commands it invokes.
If a SIGNAL_SPEC is EXIT (0) ARG is executed on exit from the shell. If
a SIGNAL_SPEC is DEBUG, ARG is executed before every simple command. If
a SIGNAL_SPEC is RETURN, ARG is executed each time a shell function or a
script run by the . or source builtins finishes executing. A SIGNAL_SPEC
of ERR means to execute ARG each time a command's failure would cause the
shell to exit when the -e option is enabled.
If no arguments are supplied, trap prints the list of commands associated
with each signal.
Options:
-l
[tab]print a list of signal names and their corresponding numbers
-p
[tab]display the trap commands associated with each SIGNAL_SPEC
Each SIGNAL_SPEC is either a signal name in <signal.h> or a signal number.
Signal names are case insensitive and the SIG prefix is optional. A
signal may be sent to the shell with "kill -signal $$".
Exit Status:
Returns success unless a SIGSPEC is invalid or an invalid option is given.
