alarm - schedule alarm signal

Syntax	#include <unistd.h> Optional #include <signal.h> (End) unsigned int alarm(unsigned int seconds);
Description	alarm() causes the system to send the calling process a SIGALRM signal after the number of real-time seconds specified by seconds have elapsed (see also signal.h). If seconds is 0, a pending alarm request, if any, is cancelled. Alarm requests are not stacked; only one SIGALRM generation can be scheduled in this manner; if the SIGALRM signal has not yet been generated, the call will result in rescheduling the time at which the SIGALRM signal will be generated. Interactions between alarm() and the functions setitimer(), ualarm() and usleep() are not defined. If threads are used, then the function affects the process or a thread in the following manner: A SIGALRM signal is generated for the process when the specified time limit has expired. BS2000 If the signal is not caught (see also signal()), the program is terminated with exit(-1). (End)
Return val.	Number of seconds until the generation of a SIGALRM signal
		if there is a previous alarm request with time remaining on the alarm clock.
	0	if there is no pending alarm request.
	alarm() is always successful.
Notes	fork() clears pending alarms in the child process. A new process image created by one of the exec functions inherits the time left to an alarm signal in the old process image. Processor scheduling delays may prevent the process from handling the signal as soon as it is generated. BS2000 SIGALRM corresponds to the STXIT event class RTIMER (real-time interval timer). (End)
See also	exec(), fork(), pause(), sigaction(), signal.h, unistd.h, section “Signals”.