NAME

     sighold, sigignore, sigpause, sigrelse, sigset — legacy interface for signal management

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <signal.h>

     int
     sighold(int sig);

     int
     sigignore(int sig);

     int
     xsi_sigpause(int sigmask);

     int
     sigrelse(int sig);

     void (*)(int)
     sigset(int, void (*disp)(int));

     int
     sigpause(int sigmask);

DESCRIPTION

     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 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 equal to
     SIG_HOLD, sig is added to the signal mask of the calling process and sig 's disposition
     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 process.

     The sigrelse() function removes sig from the signal mask of the calling process.

     The sigignore() function sets the disposition of sig to SIG_IGN.

     The 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.

     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.

RETURN VALUES

     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 error.

     For all other functions, upon successful completion, 0 is returned.  Otherwise, -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 ALSO

     kill(2), sigaction(2), sigblock(2), sigprocmask(2), sigsuspend(2), sigvec(2)

STANDARDS

     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.

HISTORY

     The sigpause() function appeared in 4.2BSD and has been deprecated.  All other functions
     appeared in FreeBSD 8.1 and were deprecated before being implemented.