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SIGHOLD(3P) POSIX Programmer's ManualSIGHOLD(3P)This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
sighold, sigignore, sigpause, sigrelse, sigset — signal management
#include <signal.h> int sighold(intsig); int sigignore(intsig); int sigpause(intsig); int sigrelse(intsig); void (*sigset(intsig, void (*disp)(int)))(int);
Use of any of these functions is unspecified in a multi-threaded process. Thesighold(),sigignore(),sigpause(),sigrelse(), andsigset() functions provide simplified signal management. Thesigset() function shall modify signal dispositions. Thesig argument specifies the signal, which may be any signal except SIGKILL and SIGSTOP. Thedisp argument specifies the signal's disposition, which may be SIG_DFL, SIG_IGN, or the address of a signal handler. Ifsigset() is used, anddisp is the address of a signal handler, the system shall addsig to the signal mask of the calling process before executing the signal handler; when the signal handler returns, the system shall restore the signal mask of the calling process to its state prior to the delivery of the signal. In addition, ifsigset() is used, anddisp is equal to SIG_HOLD,sig shall be added to the signal mask of the calling process andsig's disposition shall remain unchanged. Ifsigset() is used, anddisp is not equal to SIG_HOLD,sig shall be removed from the signal mask of the calling process. Thesighold() function shall addsig to the signal mask of the calling process. Thesigrelse() function shall removesig from the signal mask of the calling process. Thesigignore() function shall set the disposition ofsig to SIG_IGN. Thesigpause() function shall removesig from the signal mask of the calling process and suspend the calling process until a signal is received. Thesigpause() function shall restore the signal mask of the process to its original state before returning. If the action for the SIGCHLD signal is set to SIG_IGN, child processes of the calling processes shall not be transformed into zombie processes when they terminate. If the calling process subsequently waits for its children, and the process has no unwaited-for children that were transformed into zombie processes, it shall block until all of its children terminate, andwait(),waitid(), andwaitpid() shall fail and seterrno to[ECHILD].
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 anderrno set to indicate the error. Thesigpause() function shall suspend execution of the thread until a signal is received, whereupon it shall return -1 and seterrno to[EINTR]. For all other functions, upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned anderrno set to indicate the error.
These functions shall fail if:EINVALThesig argument is an illegal signal number. Thesigset() andsigignore() functions shall fail if:EINVALAn attempt is made to catch a signal that cannot be caught, or to ignore a signal that cannot be ignored.The following sections are informative.
None.
Thesigaction() function provides a more comprehensive and reliable mechanism for controlling signals; new applications should use thesigaction() function instead of the obsolescentsigset() function. Thesighold() function, in conjunction withsigrelse() orsigpause(), may be used to establish critical regions of code that require the delivery of a signal to be temporarily deferred. For broader portability, thepthread_sigmask() orsigprocmask() functions should be used instead of the obsolescentsighold() andsigrelse() functions. For broader portability, thesigsuspend() function should be used instead of the obsolescentsigpause() function.
Each of these historic functions has a direct analog in the other functions which are required to be per-thread and thread-safe (aside fromsigprocmask(), which is replaced bypthread_sigmask()). Thesigset() function can be implemented as a simple wrapper forsigaction(). Thesighold() function is equivalent tosigprocmask() orpthread_sigmask() with SIG_BLOCK set. Thesigignore() function is equivalent tosigaction() with SIG_IGN set. Thesigpause() function is equivalent tosigsuspend(). Thesigrelse() function is equivalent tosigprocmask() orpthread_sigmask() with SIG_UNBLOCK set.
These functions may be removed in a future version.
Section 2.4,Signal Concepts,exec(1p),pause(3p),pthread_sigmask(3p),sigaction(3p),signal(3p),sigsuspend(3p),wait(3p),waitid(3p) The Base Definitions volume of POSIX.1‐2017,signal.h(0p)
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online athttp://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group 2017SIGHOLD(3P)Pages that refer to this page:signal.h(0p), sigpause(3p), sigrelse(3p)
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