alarm(2)alarm(2)NAMEalarm - set a process's alarm clock
instructs the alarm clock of the calling process to send the signal to
the calling process after the number of real-time seconds specified by
sec have elapsed; see signal(5). Specific implementations might place
limitations on the maximum supported alarm time. The constant defined
in specifies the implementation-specific maximum. Whenever sec is
greater that this maximum, it is silently rounded down to it. On all
implementations, is guaranteed to be at least 31 days (in seconds).
Alarm requests are not stacked; successive calls reset the alarm clock
of the calling process.
If sec is 0, any previously made alarm request is canceled.
Alarms are not inherited by a child process across a but are inherited
On systems that support the and system calls, the timer mechanism used
by is the same as that used by Thus successive calls to and set and
return the state of a single timer. In addition, sets the timer inter‐
val to zero.
returns the amount of time previously remaining in the alarm clock of
the calling process.
In some implementations, error bounds for alarm are −1, +0 seconds (for
the posting of the alarm, not the restart of the process). Thus a
delay of 1 second can return immediately. The routine can be used to
create a more precise delay.
SEE ALSOsleep(1), exec(2), getitimer(2), pause(2), signal(5), sleep(3C).