sighold(2) DG/UX 4.30 sighold(2)
NAME
sighold - Add a signal to the calling process's set of
blocked signals.
SYNOPSIS
#include <signal.h>
int sighold (signal_number)
int signal_number;
PARAMETERS
signal_number The signal to be blocked.
DESCRIPTION
Sighold adds the specified signal to the calling process's
set of signals blocked from presentation. If the specified
signal is already blocked, no error is reported, but this
call has no effect as block operations do not nest.
It is not possible to block SIGKILL, SIGSTOP, or SIGCONT.
It may or may not be possible to block signals that are not
defined by the system. An attempt to block these signals
will produce the error EINVAL.
Note that this system call performs exactly the same basic
operation as the system call 'sigset' with the function
parameter set to SIG_HOLD and as the system call 'sigblock'
with a mask specifying a single signal. These three system
calls differ in their return values and in reporting
attempts to block a signal that cannot be blocked.
ACCESS CONTROL
None.
RETURN VALUE
0 The operation succeeded.
-1 The operation failed.
EXCEPTIONS
Errno may be set to the following error code:
EINVAL <Signal_number> is an illegal signal number
or one which may not be blocked.
SEE ALSO
The related system calls: sigset, sighold, sigrelse,
sigignore, sigpause
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