sighold(2)                     DG/UX 5.4R3.00                     sighold(2)


NAME
       sighold - add a signal to the calling process's set of blocked
       signals

SYNOPSIS
       #include <signal.h>

       int  sighold (signalnumber)
       int  signalnumber;

   where:
       signalnumber  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 or SIGSTOP.  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.

DIAGNOSTICS
       Errno may be set to the following error code:

       EINVAL    Signalnumber is an illegal signal number or one which may
                 not be blocked.

SEE ALSO
       sigignore(2), sigpause(2), sigrelse(2), sigset(2).












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