'\" te
.\" Copyright (c) 2007 Sun Microsystems, Inc.  All Rights Reserved.
.\"  Copyright 1989 AT&T
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.TH signal 3C "6 Sep 2007" "SunOS 5.11" "Standard C Library Functions"
.SH NAME
signal, sigset, sighold, sigrelse, sigignore, sigpause \- simplified signal
management for application processes
.SH SYNOPSIS
.LP
.nf
#include <signal.h>

\fBvoid\fR \fB\fR(\fB*signal(int\fR \fIsig\fR, \fBvoid (*\fR\fIdisp\fR)(int)))(int);
.fi

.LP
.nf
\fBvoid (*\fR\fBsigset\fR(\fBint\fR \fIsig\fR, \fBvoid (*\fR\fIdisp\fR)(int)))(int);
.fi

.LP
.nf
\fBint\fR \fBsighold\fR(\fBint\fR \fIsig\fR);
.fi

.LP
.nf
\fBint\fR \fBsigrelse\fR(\fBint\fR \fIsig\fR);
.fi

.LP
.nf
\fBint\fR \fBsigignore\fR(\fBint\fR \fIsig\fR);
.fi

.LP
.nf
\fBint\fR \fBsigpause\fR(\fBint\fR \fIsig\fR);
.fi

.SH DESCRIPTION
.sp
.LP
These functions provide simplified signal management for application processes.
See \fBsignal.h\fR(3HEAD) for an explanation of general signal concepts.
.sp
.LP
The \fBsignal()\fR and \fBsigset()\fR functions modify signal dispositions. The
\fIsig\fR argument specifies the signal, which may be any signal except
\fBSIGKILL\fR and  \fBSIGSTOP.\fR The \fIdisp\fR argument specifies the
signal's disposition, which may be \fBSIG_DFL,\fR \fBSIG_IGN,\fR or the address
of a signal handler. If \fBsignal()\fR is used, \fIdisp\fR is the address of a
signal handler, and \fIsig\fR is not  \fBSIGILL,\fR \fBSIGTRAP\fR, or
\fBSIGPWR\fR, the system first sets the signal's disposition to  \fBSIG_DFL\fR
before executing the signal handler. If \fBsigset()\fR is used and \fIdisp\fR
is the address of a signal handler, the system adds \fIsig\fR to the calling
process's signal  mask before executing the signal handler; when the signal
handler returns, the system restores the calling process's signal mask to its
state prior to the delivery of the signal. In addition, if \fBsigset()\fR is
used and \fIdisp\fR is equal to  \fBSIG_HOLD\fR, \fIsig\fR is added to the
calling process's signal mask and the signal's disposition remains unchanged.
.sp
.LP
The \fBsighold()\fR function adds \fIsig\fR to the calling process's signal
mask.
.sp
.LP
The \fBsigrelse()\fR function removes \fIsig\fR from the calling process's
signal mask.
.sp
.LP
The \fBsigignore()\fR function sets the disposition of \fIsig\fR to
\fBSIG_IGN.\fR
.sp
.LP
The \fBsigpause()\fR function removes \fIsig\fR from the calling process's
signal mask  and suspends the calling process until a signal is received.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBsignal()\fR returns the signal's previous
disposition. Otherwise, it returns  \fBSIG_ERR\fR and sets \fBerrno\fR to
indicate the error.
.sp
.LP
Upon successful completion, \fBsigset()\fR returns \fBSIG_HOLD\fR if the signal
had been blocked or the signal's previous disposition if it had not been
blocked. Otherwise, it returns  \fBSIG_ERR\fR and sets \fBerrno\fR to indicate
the error.
.sp
.LP
Upon successful completion, \fBsighold()\fR, \fBsigrelse()\fR,
\fBsigignore()\fR, and \fBsigpause()\fR, return  \fB0\fR. Otherwise, they
return  \fB\(mi1\fR and set  \fBerrno\fR to indicate the error.
.SH ERRORS
.sp
.LP
These functions fail if:
.sp
.ne 2
.mk
.na
\fB\fBEINTR\fR\fR
.ad
.RS 10n
.rt  
A signal was caught during the execution \fBsigpause()\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
The value of the \fIsig\fR argument is not a valid signal or is equal to
\fBSIGKILL\fR or  \fBSIGSTOP\fR.
.RE

.SH USAGE
.sp
.LP
The \fBsighold()\fR function used in conjunction with \fBsigrelse()\fR or
\fBsigpause()\fR may be used to establish critical regions of code that require
the delivery of a signal to be temporarily deferred.
.sp
.LP
If \fBsignal()\fR or \fBsigset()\fR is used to set  \fBSIGCHLD\fR's disposition
to a signal handler, \fBSIGCHLD\fR will not be sent when the calling process's
children are stopped or continued.
.sp
.LP
If any of the above functions are used to set \fBSIGCHLD\fR's disposition to
\fBSIG_IGN,\fR the calling process's child processes will not create zombie
processes when they terminate (see \fBexit\fR(2)). If the calling process
subsequently waits for its children, it blocks until all of its children
terminate; it then returns \fB\(mi1\fR with \fBerrno\fR set to \fBECHILD\fR
(see \fBwait\fR(3C) and \fBwaitid\fR(2)).
.sp
.LP
The system guarantees that if more than one instance of the same signal is
generated to a process, at least one signal will be received.  It does not
guarantee the reception of every generated signal.
.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 StabilityStandard
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBexit\fR(2), \fBkill\fR(2), \fBpause\fR(2), \fBsigaction\fR(2),
\fBsigsend\fR(2), \fBwaitid\fR(2), \fBsignal.h\fR(3HEAD), \fBwait\fR(3C),
\fBattributes\fR(5), \fBstandards\fR(5)