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sigprocmask(2)
NAME
  sigprocmask, sigsetmask - Sets the current signal mask

LIBRARY
  Standard C Library (libc)

SYNOPSIS
  #include <signal.h>

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

  The following function declaration does not conform to current standards
  and is supported only for backward compatibility:

  int sigsetmask (
	  int signal_mask );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  sigprocmask(): XSH4.2

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

PARAMETERS
  how	    Indicates the manner in which the set of masked signals is
	    changed; it has one of the following values:

	    SIG_BLOCK The resulting set is the union of the current set and
		      the signal set pointed to by the set parameter.

	    SIG_UNBLOCK
		      The resulting set is the intersection of the current
		      set and the complement of the signal set pointed to by
		      the set parameter.

	    SIG_SETMASK
		      The resulting set is the signal set pointed to by the
		      set parameter.

  set	    Specifies the signal 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.

  o_set	    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 parameter.

  signal_mask
	    [Tru64 UNIX]  Specifies the new signal mask for the process.

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

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

  If there are any unblocked signals pending after the call to the
  sigprocmask() 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 signals to
  be blocked. If a program attempts to block one of these signals, the
  sigprocmask() function gives no indication of the error.

  [Tru64 UNIX]	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) function. The signal of
  value i will be blocked if the i-th bit of signal_mask parameter is set.

EXAMPLES
  To set the signal mask to block only the SIGINT signal from delivery,
  enter:

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

RETURN VALUES
  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.

  [Tru64 UNIX]	Upon successful completion, the sigsetmask() function returns
  the value of the previous signal mask.  If the function fails, a value of
  -1 is returned.

ERRORS
  The sigprocmask() function sets errno to the specified values for the
  following conditions:

  [EINVAL]  The value of the how parameter is not equal to one of the defined
	    values.

  [EFAULT]  [Tru64 UNIX]  The set or o_set parameter points to a location
	    outside the allocated address space of the process.




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

  Standards: standards(5)

Index for Section 2

Alphabetical listing for S

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