'\" t .\" Copyright (c) 2005 by Michael Kerrisk .\" .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" .TH SIGSET 3 2005-12-01 "Linux" "Linux Programmer's Manual" .SH NAME sigset, sighold, sigrelse, sigignore \- System V signal API .SH SYNOPSIS .B #define _XOPEN_SOURCE 500 .br .B #include .sp .B typedef void (*sighandler_t)(int); .sp .BI "sighandler_t sigset(int " sig ", sighandler_t " disp ); .sp .BI "int sighold(int " sig ); .sp .BI "int sigrelse(int " sig ); .sp .BI "int sigignore(int " sig ); .SH 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 This API is obsolete: new applications should use the POSIX signal API .RB ( sigaction (2), .BR sigprocmask (2), etc.) The .BR sigset () function modifies the disposition of the signal .IR sig . The .I disp argument can be the address of a signal handler function, or one of the following constants: .TP .BR SIG_DFL Reset the disposition of .I sig to the default. .TP .BR SIG_IGN Ignore .IR sig . .TP .BR SIG_HOLD Add .I sig to the process's signal mask, but leave the disposition of .I sig unchanged. .PP If .I disp specifies the address of a signal handler, then .I sig is added to the process's signal mask during execution of the handler. .PP If .I disp was specified as a value other than .BR SIG_HOLD , then .I sig is removed from the process's signal mask. .PP The dispositions for .B SIGKILL and .B SIGSTOP cannot be changed. .PP The .BR sighold () function adds .I sig to the calling process's signal mask. The .BR sigrelse () function removes .I sig from the calling process's signal mask. The .BR sigignore () function sets the disposition of .I sig to .BR SIG_IGN . .SH RETURN VALUE On success, .BR sigset () returns .B SIG_HOLD if .I sig was blocked before the call, or the signal's previous disposition if it was not blocked before the call. On error, .BR sigset () returns \-1, with .I errno set to indicate the error. .\" FIXME . But as at 2.3.5, glibc's sigset() is broken for the .\" SIG_HOLD case: it will only return SIG_HOLD if 'disp' is .\" SIG_HOLD; if the signal is blocked, then sigset() should return .\" SIG_HOLD even if 'disp' is specified as something other than .\" SIG_HOLD (I have tested this on Solaris 8 and HP-UX 11). .\" -- mtk, 29 Nov 05 .\" See http://sourceware.org/bugzilla/show_bug.cgi?id=1951 .\" 24 Apr 06: According to Ulrich Drepper the problem is now fixed. .\" 4 Jul 06: Looking at the 20060626 glibc tree, the problem is fixed, .\" but the fix is not yet in a 2.4.x release. The .BR sighold (), .BR sigrelse (), and .BR sigignore () functions return 0 on success; on error, these functions return \-1 and set .I errno to indicate the error. .SH ERRORS For .BR sigset () see the ERRORS under .BR sigaction (2) and .BR sigprocmask (2). For .BR sighold () and .BR sigrelse () see the ERRORS under .BR sigprocmask (2). For .BR sigignore (), see the errors under .BR sigaction (2). .SH "CONFORMING TO" SVr4, POSIX.1-2001. These functions are obsolete: do not use them in new programs. .SH NOTES These functions appeared in glibc version 2.1. The .I sighandler_t type is a GNU extension; it is only used on this page to make the .BR sigset () prototype more easily readable. The .BR sigset () function provides reliable signal handling semantics (as when calling .BR sigaction (2) with .I sa_mask equal to 0). On System V, the .BR signal () function provides unreliable semantics (as when calling .BR sigaction (2) with .I sa_mask equal to .IR "SA_RESETHAND | SA_NODEFER" ). On BSD, .BR signal () provides reliable semantics. POSIX.1-2001 leaves these aspects of .BR signal () unspecified. See .BR signal (2) for further details. In order to wait for a signal, BSD and System V both provided a function named .BR sigpause (3), but this function has a different argument on the two systems. See .BR sigpause (3) for details. .SH BUGS In versions of glibc before 2.2, .BR sigset () did not unblock .I sig if .I disp was specified as a value other than .BR SIG_HOLD . In all versions of glibc up to and including 2.3.5, .BR sigset () does not correctly return the previous disposition of the signal in two cases. First, if .I disp is specified as .BR SIG_HOLD , then a successful .BR sigset () always returns .BR SIG_HOLD . Instead, it should return the previous disposition of the signal (unless the signal was blocked, in which case .BR SIG_HOLD should be returned). Second, if the signal is currently blocked, then the return value of a successful .BR sigset () should be .BR SIG_HOLD . Instead, the previous disposition of the signal is returned. .\" FIXME . This has been reported on 30 Nov 05 -- mtk .\" See http://sourceware.org/bugzilla/show_bug.cgi?id=1951 .\" .\" The POSIX.1-2001 disposition of sigset() says: .\" Upon successful completion, sigset() shall return .\" SIG_HOLD if the signal had been blocked and the signal's .\" previous disposition if it had not been blocked. .\" Otherwise, SIG_ERR shall be returned and errno set to .\" indicate the error. .SH "SEE ALSO" .BR kill (2), .BR pause (2), .BR sigaction (2), .BR signal (2), .BR sigprocmask (2), .BR raise (3), .BR sigpause (3), .BR sigvec (3), .BR feature_test_macros (7), .BR signal (7)