NAME

bsd_signal - simplified signal facilities

SYNOPSIS

[OB XSI] #include <signal.h>

void (*bsd_signal(int sig, void (*func)(int)))(int);

DESCRIPTION

The bsd_signal() function provides a partially compatible interface for programs written to historical system interfaces (see APPLICATION USAGE).

The function call bsd_signal(sig, func) shall be equivalent to the following:

void (*bsd_signal(int sig, void (*func)(int)))(int)
{
    struct sigaction act, oact;


    act.sa_handler = func;
    act.sa_flags = SA_RESTART;

    sigemptyset(&act.sa_mask);
    sigaddset(&act.sa_mask, sig);
    if (sigaction(sig, &act, &oact) == -1)
        return(SIG_ERR);

    return(oact.sa_handler);
}

The handler function should be declared:

void handler(int sig);

where sig is the signal number. The behavior is undefined if func is a function that takes more than one argument, or an argument of a different type.

RETURN VALUE

Upon successful completion, bsd_signal() shall return the previous action for sig. Otherwise, SIG_ERR shall be returned and errno shall be set to indicate the error.

ERRORS

Refer to sigaction().

EXAMPLES

None.

APPLICATION USAGE

This function is a direct replacement for the BSD signal() function for simple applications that are installing a single-argument signal handler function. If a BSD signal handler function is being installed that expects more than one argument, the application has to be modified to use sigaction(). The bsd_signal() function differs from signal() in that the SA_RESTART flag is set and the SA_RESETHAND is clear when bsd_signal() is used. The state of these flags is not specified for signal().

It is recommended that new applications use the sigaction() function.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

sigaction(), sigaddset(), sigemptyset(), signal(), the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE.

Issue 6

This function is marked obsolescent.