Manpage of SIGSET

SIGSET

Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
Index
 

NAME

sigset, sighold, sigrelse, sigignore - System V signal API  

SYNOPSIS

#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
 

DESCRIPTION

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 This API is obsolete: new applications should use the POSIX signal API (sigaction(2), sigprocmask(2), etc.)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 dispargument can be the address of a signal handler function, or one of the following constants:

SIG_DFL
Reset the disposition of sigto the default.
SIG_IGN
Ignore sig.
SIG_HOLD
Add sigto the process's signal mask, but leave the disposition of sigunchanged.

If dispspecifies the address of a signal handler, then sigis added to the process's signal mask during execution of the handler.

If dispwas specified as a value other than SIG_HOLD, then sigis removed from the process's signal mask.

The dispositions for SIGKILLand SIGSTOPcannot be changed.

The sighold() function adds sigto the calling process's signal mask.

The sigrelse() function removes sigfrom the calling process's signal mask.

The sigignore() function sets the disposition of sigto SIG_IGN.  

RETURN VALUE

On success, sigset() returns SIG_HOLDif sigwas blocked before the call, or the signal's previous disposition if it was not blocked before the call. On error, sigset() returns -1, with errnoset 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 errnoto indicate the error.  

ERRORS

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).  

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
sigset(), sighold(),
sigrelse(), sigignore()
Thread safetyMT-Safe
 

CONFORMING TO

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(), sigrelse(), and sigset() as obsolete, recommending the use of sigaction(2), sigprocmask(2), pthread_sigmask(3), and sigsuspend(2) instead.  

NOTES

These functions appeared in glibc version 2.1.

The sighandler_ttype 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_maskequal to 0).

On System V, the signal() function provides unreliable semantics (as when calling sigaction(2) with sa_maskequal 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.  

BUGS

In versions of glibc before 2.2, sigset() did not unblock sigif dispwas 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 dispis 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_HOLDshould 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.  

SEE ALSO

kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2), raise(3), sigpause(3), sigvec(3), signal(7)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
NOTES
BUGS
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 22:27:58 GMT, June 20, 2016