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

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

  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
	  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) call to block signals
  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
  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.

  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.

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.

  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 value 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.

EXAMPLES
  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);

SEE ALSO
  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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