legacy interface for signal management
Standard C Library (libc, -lc)
This interface is made obsolete by
sigset() function modifies signal
dispositions. The sig argument specifies the signal,
which may be any signal except
SIGSTOP. The disp argument
specifies the signal's disposition, which may be
SIG_IGN, or the
address of a signal handler. If
sigset() is used,
and disp is the address of a signal handler, the
system adds sig to the signal mask of the calling
process before executing the signal handler; when the signal handler
returns, the system restores the signal mask of the calling process to its
state prior to the delivery of the signal. In addition, if
sigset() is used, and disp is
SIG_HOLD, sig is
added to the signal mask of the calling process and sig
's disposition remains unchanged. If
is used, and disp is not equal to
SIG_HOLD, sig is removed from
the signal mask of the calling process.
sighold() function adds
sig to the signal mask of the calling process.
sigrelse() function removes
sig from the signal mask of the calling process.
sigignore() function sets the
disposition of sig to
xsi_sigpause() function removes
sig from the signal mask of the calling process and
suspend the calling process until a signal is received. The
xsi_sigpause() function restores the signal mask of
the process to its original state before returning.
sigpause() function assigns
sigmask to the set of masked signals and then waits
for a signal to arrive; on return the set of masked signals is restored. The
sigmask argument is usually 0 to indicate that no
signals are to be blocked.
xsi_sigpause() functions always terminate by being
interrupted, returning -1 with errno set to
Upon successful completion,
SIG_HOLD if the signal had been blocked and
the signal's previous disposition if it had not been blocked. Otherwise,
SIG_ERR is returned and errno
set to indicate the error.
For all other functions, upon successful completion, 0 is
returned. Otherwise, -1 is returned and errno is set
to indicate the error:
- The sig argument is not a valid signal number.
sigignore() functions, an attempt was made to
catch or ignore
sigpause() function is implemented for compatibility
with historic 4.3BSD applications. An incompatible
interface by the same name, which used a single signal number rather than a
mask, was present in AT&T System V UNIX,
and was copied from there into the X/Open System Interfaces
(XSI) option of IEEE Std 1003.1-2001
(“POSIX.1”). FreeBSD implements
it under the name
functions are implemented for compatibility with System V
and XSI interfaces.
sigpause() function appeared in
4.2BSD and has been deprecated. All other functions
appeared in FreeBSD 8.1 and were deprecated before