NAME
sigblock —
block signals
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <signal.h>
int
sigblock(
int
mask);
int
sigmask(
signum);
DESCRIPTION
sigblock() adds the signals specified in
mask to the set of signals currently being blocked from
delivery. Signals are blocked if the corresponding bit in
mask is a 1; the macro
sigmask() is
provided to construct the mask for a given
signum.
It is not possible to block
SIGKILL
or
SIGSTOP
; this restriction is silently imposed by the
system.
RETURN VALUES
The previous set of masked signals is returned.
EXAMPLES
The following example using
sigblock():
int omask;
omask = sigblock(sigmask(SIGINT) | sigmask(SIGHUP));
Becomes:
sigset_t set, oset;
sigemptyset(&set);
sigaddset(&set, SIGINT);
sigaddset(&set, SIGHUP);
sigprocmask(SIG_BLOCK, &set, &oset);
Another use of
sigblock() is to get the current set of masked
signals without changing what is actually blocked. Instead of:
int set;
set = sigblock(0);
Use the following:
sigset_t set;
sigprocmask(SIG_BLOCK, NULL, &set);
SEE ALSO
kill(2),
sigaction(2),
sigprocmask(2),
sigsetmask(3),
sigsetops(3)
HISTORY
The
sigblock() function call appeared in
4.2BSD and has been deprecated.