NAME

sigprocmask - Examine and change blocked signals (POSIX software signal facilities)

SYNOPSIS

#include <signal.h> int sigprocmask(int how, const sigset_t *set, sigset_t *oset);

PARAMETERS

howThe manner in which the values in set are changed as defined by one of the argument values described below. 

setA set of signals that will be used to change the current thread’s signal mask according to the value in the how parameter. 

osetPoints to a location in which the signal mask in effect at the time of the sigprocmask() function call is returned.

DESCRIPTION

The sigprocmask() function is used to examine or change (or both) the signal mask of the calling process. If the value of the argument set is not NULL, it points to a set of signals to be used to change the currently blocked set according to the how parameter as follows:

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

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

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

If the argument oset is not NULL, the previous mask is stored in the space pointed to by oset.  The sigprocmask() function can be used to inquire about the currently blocked signals by specifying a null pointer for set, since the value of the argument how is not significant and the signal mask of the process is unchanged unless this parameter is not a null pointer. In order for the signal mask in effect at the time of the sigprocmask() call to be returned, the oset argument must not be a null pointer. If there are any pending unblocked signals after  the call to the sigprocmask() function, at least one of those signals shall be delivered before the sigprocmask() function returns. As a system restriction, the SIGKILL and SIGSTOP signals cannot be blocked. If the sigprocmask() function fails, the signal mask of the process is not changed by this function call.

RETURN VALUES

Possible return values are as follows:

RELATED INFORMATION

Functions: sigaction(3), sigpending(3), sigsetops(3), sigsuspend(3). 

Hewlett-Packard Company  —  OSF DCE 1.1/HP DCE 1.5