sigprocmask(2)            SYSTEM CALLS             sigprocmask(2)



NAME
     sigprocmask - change or examine signal mask

SYNOPSIS
     #include <signal.h>

     int  sigprocmask(int  how,  const  sigsett  *set,  sigsett
     *oset);

DESCRIPTION
     The sigprocmask function is used to  examine  and/or  change
     the   calling  process's  signal  mask.   If  the  value  is
     SIGBLOCK, the set pointed to by the argument set  is  added
     to  the  current  signal mask.  If the value is SIGUNBLOCK,
     the set pointed by the argument  set  is  removed  from  the
     current  signal  mask.   If  the  value  is SIGSETMASK, the
     current signal mask is replaced by the set pointed to by the
     argument  set.  If the argument oset is not NULL, the previ-
     ous mask is stored in the space pointed to by oset.  If  the
     value of the argument set is NULL, the value how is not sig-
     nificant and the process's signal mask is  unchanged;  thus,
     the call can be used to enquire about currently blocked sig-
     nals.

     If there are any pending unblocked signals after the call to
     sigprocmask, at least one of those signals will be delivered
     before the call to sigprocmask returns.

     It is not possible to block those  signals  that  cannot  be
     ignored  [see  sigaction(2)];  this  restriction is silently
     imposed by the system.

     If sigprocmask fails,  the  process's  signal  mask  is  not
     changed.

     sigprocmask fails if any of the following is true:

     EINVAL         The value of the how argument is not equal to
                    one of the defined values.

     EFAULT         The value of set or oset points  outside  the
                    process's allocated address space.

SEE ALSO
     sigaction(2), signal(2), sigsetopts(3C), signal(5).

DIAGNOSTICS
     On  success,  sigprocmask  returns  zero.   On  failure,  it
     returns -1 and sets errno to indicate the error.






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