Unix signals

UNIX signals

Number	KSH Name	Description
0	EXIT	This number does not correspond to a real signal, but the corresponding trap is executed before script termination.
1	HUP	hangup
2	INT	The interrupt signal typically is generated using the DEL or the ^C key
3	QUIT	The quit signal is typically generated using the ^[ key. It is used like the INT signal but explicitly requests a core dump.
4	ILL	illegal instruction
5	TRAP	trace trap
6	IOT	IOT instruction
7	EMT	EMT instruction
8	FPE	floating point exception
9	KILL	cannot be caught or ignored
10	BUS	bus error
11	SEGV	segmentation violation
12	SYS	bad argument to system call
13	PIPE	generated if there is a pipeline without reader to terminate the writing process(es)
14	ALRM	alarm clock
15	TERM	generated to terminate the process gracefully
16	USR1	user defined signal 1
17	USR2	user defined signal 2
18	CLD	child process died
19	PWR	restart after power failure
-	DEBUG	KSH only: This is no signal, but the corresponding trap code is executed before each statement of the script.

Usage: KSH script
Use "trap" function to catch the signals in shell script:


print -n "Enter Your password:"
stty_orig=`stty -g`
trap "stty ${stty_orig}; exit" 1 2 3 15
stty -echo >&- 2>&-
read PASS 
stty ${stty_orig} >&- 2>&-
trap 1 2 3 15
print

Perl


# Just ignore the interruption
$SIG{'INT'} = 'IGNORE'; 
# ...some code...
$SIG{'INT'} = 'DEFAULT'; 
################
# Complex processing
sub INT_handler {
 # some actions, ie writing to the log
 exit(0);
}
$SIG{'INT'} = 'INT_handler';