PTHREAD_SIGMASK(3P)                                 POSIX Programmer's Manual                                PTHREAD_SIGMASK(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       pthread_sigmask, sigprocmask - examine and change blocked signals

SYNOPSIS
       #include <signal.h>



       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);


DESCRIPTION
       The pthread_sigmask() function shall examine or change (or both) the calling thread's signal mask, regardless of the num-
       ber of threads in the process. The function shall be equivalent to sigprocmask(), without the restriction that  the  call
       be made in a single-threaded process.

       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:

       SIG_BLOCK
              The resulting set shall be the union of the current set and the signal set pointed to by set.

       SIG_SETMASK
              The resulting set shall be the signal set pointed to by set.

       SIG_UNBLOCK
              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 location 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 deliv-
       ered 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.

RETURN VALUE
       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.

ERRORS
       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.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       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 function overrides that change (see sigaction()). If the signal-catch-
       ing function was installed with signal(), it is unspecified whether this occurs.

       See kill() for a discussion of the requirement on delivery of signals.

FUTURE DIRECTIONS
       None.

SEE ALSO
       sigaction(), sigaddset(), sigdelset(), sigemptyset(),  sigfillset(),  sigismember(),  sigpending(),  sigqueue(),  sigsus-
       pend(), the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>

COPYRIGHT
       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,  Copy-
       right (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   original   Standard   can   be   obtained  online  at  http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                           PTHREAD_SIGMASK(3P)