Current File : //usr/share/man/man2/alarm.2

'\" te
.\" Copyright (c) 2007, Sun Microsystems, Inc.  All Rights Reserved.
.\" Copyright 1989 AT&T.
.TH alarm 2 "6 Jun 2007" "SunOS 5.11" "System Calls"
.SH NAME
alarm \- schedule an alarm signal
.SH SYNOPSIS
.LP
.nf
#include <unistd.h>

\fBunsigned int\fR \fBalarm\fR(\fBunsigned int\fR \fIseconds\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBalarm()\fR function causes the system to generate a \fBSIGALRM\fR signal for the process after the number of real-time seconds specified by seconds  have  elapsed (see  \fBsignal.h\fR(3HEAD)). Processor scheduling delays may prevent the process from handling the signal as soon as it is generated.
.sp
.LP
If \fIseconds\fR is 0, a pending alarm request, if any, is cancelled. If \fIseconds\fR is greater than \fBLONG_MAX\fR/\fIhz\fR, \fIseconds\fR is rounded down to \fBLONG_MAX\fR/\fIhz\fR. The value of \fIhz\fR is normally 100.
.sp
.LP
Alarm requests are not stacked; only one \fBSIGALRM\fR  generation can  be  scheduled in this manner; if the \fBSIGALRM\fR signal has not yet been generated, the call will result in rescheduling the time at which the \fBSIGALRM\fR signal will be generated.
.sp
.LP
The \fBfork\fR(2) function clears pending alarms in the child process. A new process image created by one of the \fBexec\fR(2) functions inherits the time left to an alarm signal in the old process's image.
.SH RETURN VALUES
.sp
.LP
If there is a previous alarm request with time  remaining, \fBalarm()\fR returns  a  non-zero  value  that  is the number of seconds until the previous request would  have  generated  a \fBSIGALRM\fR signal.  Otherwise, \fBalarm()\fR returns 0.
.SH ERRORS
.sp
.LP
The \fBalarm()\fR function is always successful; no return value is reserved to indicate an error.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelAsync-Signal-Safe
_
StandardSee \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBexec\fR(2), \fBfork\fR(2), \fBsignal.h\fR(3HEAD), \fBattributes\fR(5), \fBstandards\fR(5)