sigprocmask man page on DigitalUNIX

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sigprocmask(2)							sigprocmask(2)

       sigprocmask, sigsetmask - Set the current signal mask

       #include <signal.h>

       int sigprocmask(
	       int how,
	       const sigset_t *set,
	       sigset_t *o_set );

       The  following  function	 declaration does not conform to current stan‐
       dards and is supported only for backward compatibility: int sigsetmask(
	       int signal_mask );

       Interfaces documented on this reference page conform to industry	 stan‐
       dards as follows:

       sigprocmask(): XSH4.0, XSH4.2, XSH5.0

       Refer  to  the  standards(5)  reference page for more information about
       industry standards and associated tags.

       Indicates the manner in which the set of masked signals is changed;  it
       has  one of the following values: The resulting set is the union of the
       current set and the signal set pointed to by the	 set  parameter.   The
       resulting set is the intersection of the current set and the complement
       of the signal set pointed to by the set parameter.  The	resulting  set
       is  the signal set pointed to by the set parameter.  Specifies the sig‐
       nal set. If the value of the set parameter is not null, it points to  a
       set  of signals to be used to change the currently blocked set.	If the
       value of the set parameter is null, the value of the how	 parameter  is
       not  significant	 and  the  process signal mask is unchanged; thus, the
       call can be used to inquire about currently blocked  signals.   If  the
       o_set parameter is not the null value, the signal mask in effect at the
       time of the call is stored in the space pointed to by the o_set parame‐
       ter.  Specifies the new signal mask for the process.

       The sigprocmask() function is used to examine or change the signal mask
       of the calling process.

       Typically, you would use the sigprocmask (SIG_BLOCK) call to block sig‐
       nals  during  a	critical section of code, and then use the sigprocmask
       (SIG_SETMASK) call to restore the mask to the previous  value  returned
       by the sigprocmask (SIG_BLOCK) call.

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

       The  sigprocmask()  function does not allow the SIGKILL or SIGSTOP sig‐
       nals to be blocked. If a program attempts to block one  of  these  sig‐
       nals, the sigprocmask() function gives no indication of the error.

       The  sigsetmask() function allows the process signal mask to change for
       signal values 1 to 31. This same function can be accomplished  for  all
       values  with  the sigprocmask(SIG_SETMASK) call.	 The signal of value i
       will be blocked if the i-th bit of the signal_mask parameter is set.

       Upon successful completion, the sigprocmask() function returns a	 value
       of  0  (zero).  If the sigprocmask() function fails, the signal mask of
       the process is unchanged, a value of -1 is returned, and errno  is  set
       to indicate the error.

       Upon successful completion, the sigsetmask() function returns the value
       of the previous signal mask. If the function fails, a value  of	-1  is

       The  sigprocmask()  function  sets errno to the specified value for the
       following conditions: The value of the how parameter is	not  equal  to
       one  of	the  defined values.  [Tru64 UNIX]  The set or o_set parameter
       points to a  location  outside  the  allocated  address	space  of  the

       The  following  example	sets  the signal mask to block only the SIGINT
       signal from delivery:

       #include <signal.h> int return_value; sigset_t newset;
	...  sigemptyset(&newset); sigaddset(&newset, SIGINT); return_value  =
       sigprocmask (SIG_SETMASK, &newset, NULL);

       Functions: kill(2), sigaction(2), sigsuspend(2), sigvec(2), sigpause(3)

       Standards: standards(5)


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