alarm.2

unix v7是最后一个广泛发布的研究型UNIX版本

.TH ALARM 2 
.SH NAME
alarm \- schedule signal after specified time
.SH SYNOPSIS
.B alarm(seconds)
.br
.B unsigned seconds;
.SH DESCRIPTION
.I Alarm
causes signal SIGALRM, see
.IR signal (2),
to be sent to the invoking process
in a number of seconds given by the argument.
Unless caught or ignored, the signal terminates the process.
.PP
Alarm requests are not stacked;
successive calls reset the alarm clock.
If the argument is 0, any alarm request is cancelled.
Because the clock has a 1-second resolution,
the signal may occur up to one second early;
because of scheduling delays,
resumption of execution of when the signal is
caught may be delayed an arbitrary amount.
The longest specifiable delay time is 65535 seconds.
.PP
The return value is the amount of time
previously remaining in the alarm clock.
.SH "SEE ALSO"
pause(2), signal(2), sleep(3)
.SH ASSEMBLER
(alarm = 27.)
.br
(seconds in r0)
.br
.B sys alarm
.br
(previous amount in r0)