SIGPAUSE(2) BSD System Calls Manual SIGPAUSE(2)NAME
sighold, sigignore, sigpause, sigrelse, sigset — legacy interface for
Standard C Library (libc, -lc)
sigset(int, void (*disp)(int));
This interface is made obsolete by sigsuspend(2) and sigaction(2)
The sigset() function modifies signal dispositions. The sig argument
specifies the signal, which may be any signal except SIGKILL and SIGSTOP.
The disp argument specifies the signal's disposition, which may be
SIG_DFL, 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 han‐
dler; 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 equal to SIG_HOLD,
sig is added to the signal mask of the calling process and sig 's dispo‐
sition remains unchanged. If sigset() is used, and disp is not equal to
SIG_HOLD, sig is removed from the signal mask of the calling process.
The sighold() function adds sig to the signal mask of the calling
The sigrelse() function removes sig from the signal mask of the calling
The sigignore() function sets the disposition of sig to SIG_IGN.
The xsi_sigpause() function removes sig from the signal mask of the call‐
ing 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.
The 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.
The sigpause() and xsi_sigpause() functions always terminate by being
interrupted, returning -1 with errno set to EINTR.
Upon successful completion, sigset() returns 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
For all other functions, upon successful completion, 0 is returned. Oth‐
erwise, -1 is returned and errno is set to indicate the error:
[EINVAL] The sig argument is not a valid signal number.
[EINVAL] For sigset() and sigignore() functions, an attempt was
made to catch or ignore SIGKILL or SIGSTOP.
SEE ALSOkill(2), sigaction(2), sigblock(2), sigprocmask(2), sigsuspend(2),
The 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 xsi_sigpause(). The sighold(), sigignore(),
sigrelse() and sigset() functions are implemented for compatibility with
System V and XSI interfaces.
The sigpause() function appeared in 4.2BSD and has been deprecated. All
other functions appeared in FreeBSD 8.1 and were deprecated before being
BSD June 2, 1993 BSD