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.\"     @(#)sigpause.2	8.1 (Berkeley) 6/2/93
.\" $FreeBSD: releng/12.0/lib/libc/compat-43/sigpause.2 314436 2017-02-28 23:42:47Z imp $
.\"
.\" Part of the content of the man page was derived from
.\" The Open Group Base Specifications Issue 7
.\" IEEE Std 1003.1-2008
.\"
.Dd June 2, 1993
.Dt SIGPAUSE 2
.Os
.Sh NAME
.Nm sighold ,
.Nm sigignore ,
.Nm sigpause ,
.Nm sigrelse ,
.Nm sigset
.Nd legacy interface for signal management
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In signal.h
.Ft int
.Fn sighold "int sig"
.Ft int
.Fn sigignore "int sig"
.Ft int
.Fn xsi_sigpause "int sigmask"
.Ft int
.Fn sigrelse "int sig"
.Ft void (*)(int)
.Fn sigset "int" "void (*disp)(int)"
.Ft int
.Fn sigpause "int sigmask"
.Sh DESCRIPTION
.Sy This interface is made obsolete by
.Xr sigsuspend 2
.Sy and
.Xr sigaction 2 .
.Pp
The
.Fn sigset
function modifies signal dispositions.
The
.Fa sig
argument specifies the signal, which may be any signal except
.Dv SIGKILL
and
.Dv SIGSTOP .
The
.Fa disp
argument specifies the signal's disposition,
which may be
.Dv SIG_DFL ,
.Dv SIG_IGN ,
or the address of a signal handler.
If
.Fn sigset
is used, and
.Fa disp
is the address of a signal handler, the
system adds
.Fa sig
to the signal mask of the calling process before executing the signal
handler; when the signal handler returns, the system restores the
signal mask of the calling process to its state prior to the delivery
of the signal.
In addition, if
.Fn sigset
is used, and
.Fa disp
is equal to
.Dv SIG_HOLD ,
.Fa sig
is added to the signal
mask of the calling process and
.Fa sig 's
disposition remains unchanged.
If
.Fn sigset
is used, and
.Fa disp
is not equal to
.Dv SIG_HOLD ,
.Fa sig
is removed from the signal mask of the calling process.
.Pp
The
.Fn sighold
function adds
.Fa sig
to the signal mask of the calling process.
.Pp
The
.Fn sigrelse
function removes
.Fa sig
from the signal mask of the calling process.
.Pp
The
.Fn sigignore
function sets the disposition of
.Fa sig
to
.Dv SIG_IGN .
.Pp
The
.Fn xsi_sigpause
function removes
.Fa sig
from the signal mask of the calling process and suspend the calling process
until a signal is received.
The
.Fn xsi_sigpause
function restores the signal mask of the process to its original state before
returning.
.Pp
The
.Fn sigpause
function
assigns
.Fa sigmask
to the set of masked signals
and then waits for a signal to arrive;
on return the set of masked signals is restored.
The
.Fa sigmask
argument
is usually 0 to indicate that no
signals are to be blocked.
.Sh RETURN VALUES
The
.Fn sigpause
and
.Fn xsi_sigpause
functions
always terminate by being interrupted, returning -1 with
.Va errno
set to
.Er EINTR .
.Pp
Upon successful completion,
.Fn sigset
returns
.Dv SIG_HOLD
if the signal had been blocked and the signal's previous disposition if
it had not been blocked.
Otherwise,
.Dv SIG_ERR
is returned and
.Va errno
set to indicate the error.
.Pp
For all other functions, upon successful completion, 0 is returned.
Otherwise, -1 is returned and
.Va errno
is set to indicate the error:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa sig
argument
is not a valid signal number.
.It Bq Er EINVAL
For
.Fn sigset
and
.Fn sigignore
functions, an attempt was made to catch or ignore
.Dv SIGKILL
or
.Dv SIGSTOP .
.El
.Sh SEE ALSO
.Xr kill 2 ,
.Xr sigaction 2 ,
.Xr sigblock 2 ,
.Xr sigprocmask 2 ,
.Xr sigsuspend 2 ,
.Xr sigvec 2
.Sh STANDARDS
The
.Fn sigpause
function is implemented for compatibility with historic
.Bx 4.3
applications.
An incompatible interface by the same name, which used a single signal number
rather than a mask, was present in
.At V ,
and was copied from there into the
.Sy X/Open System Interfaces
.Pq Tn XSI
option of
.St -p1003.1-2001 .
.Fx
implements it under the name
.Fn xsi_sigpause .
The
.Fn sighold ,
.Fn sigignore ,
.Fn sigrelse
and
.Fn sigset
functions are implemented for compatibility with
.Sy System V
and
.Sy XSI
interfaces.
.Sh HISTORY
The
.Fn sigpause
function appeared in
.Bx 4.2
and has been deprecated.
All other functions appeared in
.Fx 8.1
and were deprecated before being implemented.