sigprocmask(2) System Calls Manual 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
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 com-
plement 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. [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 sigproc-
mask (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 sig-
nals, 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 sig-
nal_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: 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.
RELATED INFORMATION
Functions: kill(2), sigaction(2), sigsuspend(2), sigvec(2), sigpause(3)
Standards: standards(5) delim off
sigprocmask(2)