alarm(2) -- Linux man page
NAMEalarm - set an alarm clock for delivery of a signal
#include <unistd.h> unsigned int alarm(unsigned int seconds);
DESCRIPTIONalarm arranges for a SIGALRM signal to be delivered to the process in seconds seconds.
If seconds is zero, no new alarm is scheduled.
RETURN VALUEalarm returns the number of seconds remaining until any previously scheduled alarm was due to be delivered, or zero if there was no previously scheduled alarm.
NOTESalarm and setitimer share the same timer; calls to one will interfere with use of the other.
sleep() may be implemented using SIGALRM; mixing calls to alarm() and sleep() is a bad idea.
CONFORMING TOSVr4, SVID, POSIX, X/OPEN, BSD 4.3
SEE ALSOsetitimer(2), signal(2), sigaction(2), gettimeofday(2), select(2), pause(2), sleep(3)