sigprocmask, sigsetmask - Set the current signal mask
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 signal_mask );
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.
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 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. 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.
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 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
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
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
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
Upon successful completion, the sigsetmask() function
returns the value of the previous signal mask. If the
function fails, a value of -1 is returned.
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 process.
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),
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