NAME
sigset, sighold, sigrelse, sigignore - System V signal API SYNOPSIS
#include
typedef void (*sighandlert)(int); sighandlert sigset(int sig, sighandlert disp); int sighold(int sig); int sigrelse(int sig); int sigignore(int sig); Feature Test Macro Requirements for glibc (see featuretestmacros(7)): sigset(), sighold(), sigrelse(), sigignore(): XOPENSOURCE >= 500 || XOPENSOURCE && XOPENSOURCEEXTENDED 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 This API is obsolete: new applications should use the POSIX signal API (sigac‐ tion(2), sigprocmask(2), etc.)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: SIGDFL Reset the disposition of sig to the default. SIGIGN Ignore sig. SIGHOLD 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 SIGHOLD, 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 SIGIGN. RETURN VALUE On success, sigset() returns SIGHOLD 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 suc‐
cess; on error, these functions return -1 and set errno to 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). ┌────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├────────────────────────┼───────────────┼─────────┤
│sigset(), sighold(), │ Thread safety │ MT-Safe │ │sigrelse(), sigignore() │ │ │ └────────────────────────┴───────────────┴─────────┘ CONFORMING TO
SVr4, POSIX.1-2001. 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 sigac‐ tion(2), sigprocmask(2), pthreadsigmask(3), and sigsuspend(2) instead. NOTES These functions appeared in glibc version 2.1. The sighandlert 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 samask equal to 0). On System V, the signal() function provides unreliable semantics (as when calling sigaction(2) with samask equal to SARESETHAND | SANODE‐
FER). On BSD, signal() provides reliable semantics. POSIX.1-2001 leaves these aspects of signal() unspecified. See signal(2) for fur‐ ther details. In order to wait for a signal, BSD and System V both provided a func‐ tion 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 sig if disp was specified as a value other than SIGHOLD. 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 SIGHOLD, then a successful sigset() always returns SIGHOLD. Instead, it should return the previous disposition of the signal (unless the signal was blocked, in which case SIGHOLD should be returned). Second, if the signal is currently blocked, then the return value of a successful sigset() should be SIGHOLD. Instead, the previ‐ ous 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) COLOPHON
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Linux 2010-09-20 SIGSET(3)