trusty (3) pthread_sigmask.3posix.gz

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  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 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 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() , sigsuspend() , 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, 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 .