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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 (consult 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 number 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  sig-
       nals 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'  sig-
       nal 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  sigproc-
       mask(),  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.
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-catching function was installed  with  sig-
       nal(), 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(), sigsuspend(), the Base Defini-
       tions 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, 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 original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                  PTHREAD_SIGMASK(3P)