PTHREAD_SIGMASK(P) POSIX Programmer's Manual PTHREAD_SIGMASK(P)
pthread_sigmask, sigprocmask - examine and change blocked signals
int pthread_sigmask(int how, const sigset_t *restrict set,
sigset_t *restrict oset);
int sigprocmask(int how, const sigset_t *restrict set,
sigset_t *restrict oset);
The pthread_sigmask() function shall examine or change (or both) the calling thread's sig-
nal mask, regardless of the number of threads in the process. The function shall be equiv-
alent to sigprocmask(), without the restriction that the call be made in a single-threaded
In a single-threaded process, the sigprocmask() function shall examine or change (or both)
the signal mask of the calling thread.
If the argument set is not a null pointer, it points to a set of signals to be used to
change the currently blocked set.
The argument how indicates the way in which the set is changed, and the application shall
ensure it consists of one of the following values:
The resulting set shall be the union of the current set and the signal set pointed
to by set.
The resulting set shall be the signal set pointed to by set.
The resulting set shall be the intersection of the current set and the complement
of the signal set pointed to by set.
If the argument oset is not a null pointer, the previous mask shall be stored in the loca-
tion pointed to by oset. If set is a null pointer, the value of the argument how is not
significant and the process' signal mask shall be unchanged; thus the call can be used to
enquire about currently blocked signals.
If there are any pending unblocked signals after the call to sigprocmask(), at least one
of those signals shall be delivered before the call to sigprocmask() returns.
It is not possible to block those signals which cannot be ignored. This shall be enforced
by the system without causing an error to be indicated.
If any of the SIGFPE, SIGILL, SIGSEGV, or SIGBUS signals are generated while they are
blocked, the result is undefined, unless the signal was generated by the kill() function,
the sigqueue() function, or the raise() function.
If sigprocmask() fails, the thread's signal mask shall not be changed.
The use of the sigprocmask() function is unspecified in a multi-threaded process.
Upon successful completion pthread_sigmask() shall return 0; otherwise, it shall return
the corresponding error number.
Upon successful completion, sigprocmask() shall return 0; otherwise, -1 shall be returned,
errno shall be set to indicate the error, and the process' signal mask shall be unchanged.
The pthread_sigmask() and sigprocmask() functions shall fail if:
EINVAL The value of the how argument is not equal to one of the defined values.
The pthread_sigmask() function shall not return an error code of [EINTR].
The following sections are informative.
When a process' signal mask is changed in a signal-catching function that is installed by
sigaction(), the restoration of the signal mask on return from the signal-catching func-
tion overrides that change (see sigaction()). If the signal-catching function was
installed with signal(), it is unspecified whether this occurs.
See kill() for a discussion of the requirement on delivery of signals.
sigaction() , sigaddset() , sigdelset() , sigemptyset() , sigfillset() , sigismember() ,
sigpending() , sigqueue() , sigsuspend() , the Base Definitions volume of
IEEE Std 1003.1-2001, <signal.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 PTHREAD_SIGMASK(P)