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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON |
SIGSET(3) Linux Programmer's Manual SIGSET(3)
sigset, sighold, sigrelse, sigignore - System V signal API
#include <signal.h>
typedef void (*sighandler_t)(int);
sighandler_t sigset(int sig, sighandler_t disp);
int sighold(int sig);
int sigrelse(int sig);
int sigignore(int sig);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sigset(), sighold(), sigrelse(), sigignore():
_XOPEN_SOURCE >= 500
These functions are provided in glibc as a compatibility interface
for programs that make use of the historical System V signal API.
This API is obsolete: new applications should use the POSIX signal
API (sigaction(2), sigprocmask(2), etc.)
The sigset() function modifies the disposition of the signal sig.
The disp argument can be the address of a signal handler function, or
one of the following constants:
SIG_DFL
Reset the disposition of sig to the default.
SIG_IGN
Ignore sig.
SIG_HOLD
Add sig to the process's signal mask, but leave the
disposition of sig unchanged.
If disp specifies the address of a signal handler, then sig is added
to the process's signal mask during execution of the handler.
If disp was specified as a value other than SIG_HOLD, then sig is
removed from the process's signal mask.
The dispositions for SIGKILL and SIGSTOP cannot be changed.
The sighold() function adds sig to the calling process's signal mask.
The sigrelse() function removes sig from the calling process's signal
mask.
The sigignore() function sets the disposition of sig to SIG_IGN.
On success, sigset() returns SIG_HOLD if sig was blocked before the
call, or the signal's previous disposition if it was not blocked
before the call. On error, sigset() returns -1, with errno set to
indicate the error. (But see BUGS below.)
The sighold(), sigrelse(), and sigignore() functions return 0 on
success; on error, these functions return -1 and set errno to
indicate the error.
For sigset() see the ERRORS under sigaction(2) and sigprocmask(2).
For sighold() and sigrelse() see the ERRORS under sigprocmask(2).
For sigignore(), see the errors under sigaction(2).
For an explanation of the terms used in this section, see
attributes(7).
┌────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────┼───────────────┼─────────┤
│sigset(), sighold(), │ Thread safety │ MT-Safe │
│sigrelse(), sigignore() │ │ │
└────────────────────────┴───────────────┴─────────┘
SVr4, POSIX.1-2001, POSIX.1-2008. These functions are obsolete: do
not use them in new programs. POSIX.1-2008 marks sighold(),
sigignore(), sigpause(3), sigrelse(), and sigset() as obsolete,
recommending the use of sigaction(2), sigprocmask(2),
pthread_sigmask(3), and sigsuspend(2) instead.
These functions appeared in glibc version 2.1.
The sighandler_t type is a GNU extension; it is used on this page
only to make the sigset() prototype more easily readable.
The sigset() function provides reliable signal handling semantics (as
when calling sigaction(2) with sa_mask equal to 0).
On System V, the signal() function provides unreliable semantics (as
when calling sigaction(2) with sa_mask equal to SA_RESETHAND |
SA_NODEFER). On BSD, signal() provides reliable semantics.
POSIX.1-2001 leaves these aspects of signal() unspecified. See
signal(2) for further details.
In order to wait for a signal, BSD and System V both provided a
function named sigpause(3), but this function has a different
argument on the two systems. See sigpause(3) for details.
In versions of glibc before 2.2, sigset() did not unblock sig if disp
was specified as a value other than SIG_HOLD.
In versions of glibc before 2.5, sigset() does not correctly return
the previous disposition of the signal in two cases. First, if disp
is specified as SIG_HOLD, then a successful sigset() always returns
SIG_HOLD. Instead, it should return the previous disposition of the
signal (unless the signal was blocked, in which case SIG_HOLD should
be returned). Second, if the signal is currently blocked, then the
return value of a successful sigset() should be SIG_HOLD. Instead,
the previous disposition of the signal is returned. These problems
have been fixed since glibc 2.5.
kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2), raise(3),
sigpause(3), sigvec(3), signal(7)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2016-03-15 SIGSET(3)
Pages that refer to this page: sigvec(3), signal(7), signal-safety(7)