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[thirdparty/man-pages.git] / man3 / sigpause.3

.\" Copyright (C) 2004 Andries Brouwer (aeb@cwi.nl)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH sigpause 3 (date) "Linux man-pages (unreleased)"
.SH NAME
sigpause \- atomically release blocked signals and wait for interrupt
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <signal.h>
.PP
.BI "int sigpause(int " sigmask ");  /* BSD (but see NOTES) */"
.PP
.BI "int sigpause(int " sig ");      /* System V / UNIX 95 */"
.fi
.SH DESCRIPTION
Don't use this function.
Use
.BR sigsuspend (2)
instead.
.PP
The function
.BR sigpause ()
is designed to wait for some signal.
It changes the process's signal mask (set of blocked signals),
and then waits for a signal to arrive.
Upon arrival of a signal, the original signal mask is restored.
.SH RETURN VALUE
If
.BR sigpause ()
returns, it was interrupted by a signal and the return value is \-1
with
.I errno
set to
.BR EINTR .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR sigpause ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.\" FIXME: The marking is different from that in the glibc manual,
.\" marking in glibc manual is more detailed:
.\"
.\" sigpause: MT-Unsafe race:sigprocmask/!bsd!linux
.\"
.\" glibc manual says /!linux!bsd indicate the preceding marker only applies
.\" when the underlying kernel is neither Linux nor a BSD kernel.
.\" So, it is safe in Linux kernel.
.SH STANDARDS
The System V version of
.BR sigpause ()
is standardized in POSIX.1-2001.
It is also specified in POSIX.1-2008, where it is marked obsolete.
.SH NOTES
.SS History
The classical BSD version of this function appeared in 4.2BSD.
It sets the process's signal mask to
.IR sigmask .
UNIX 95 standardized the incompatible System V version of
this function, which removes only the specified signal
.I sig
from the process's signal mask.
.\" __xpg_sigpause: UNIX 95, spec 1170, SVID, SVr4, XPG
The unfortunate situation with two incompatible functions with the
same name was solved by the
.BR \%sigsuspend (2)
function, that takes a
.I "sigset_t\ *"
argument (instead of an
.IR int ).
.SS Linux notes
On Linux, this routine is a system call only on the Sparc (sparc64)
architecture.
.PP
.\" Libc4 and libc5 know only about the BSD version.
.\"
Glibc uses the BSD version if the
.B _BSD_SOURCE
feature test macro is defined and none of
.BR _POSIX_SOURCE ,
.BR _POSIX_C_SOURCE ,
.BR _XOPEN_SOURCE ,
.BR _GNU_SOURCE ,
or
.B _SVID_SOURCE
is defined.
Otherwise, the System V version is used,
and feature test macros must be defined as follows to obtain the declaration:
.IP \(bu 3
Since glibc 2.26:
_XOPEN_SOURCE >= 500
.\" || (_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED)
.IP \(bu
Glibc 2.25 and earlier: _XOPEN_SOURCE
.PP
Since glibc 2.19, only the System V version is exposed by
.IR <signal.h> ;
applications that formerly used the BSD
.BR sigpause ()
should be amended to use
.BR sigsuspend (2).
.\"
.\" For the BSD version, one usually uses a zero
.\" .I sigmask
.\" to indicate that no signals are to be blocked.
.SH SEE ALSO
.BR kill (2),
.BR sigaction (2),
.BR sigprocmask (2),
.BR sigsuspend (2),
.BR sigblock (3),
.BR sigvec (3),
.BR feature_test_macros (7)