Reliable management of signal SIGPIPE and SIGTERM Post: 302406362

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Top Forums Programming Reliable management of signal SIGPIPE and SIGTERM Post 302406362 by Loic Domaigne on Monday 22nd of March 2010 04:45:50 PM

03-22-2010

Registered User

Quote:

Originally Posted by italian_boy

I' m note very expert in the reliable manage of signal... but in my server I must manage SIGPIPE for the socket and SIGTERM...
I've wrote this but there is something wrong... Can someone explain me with some example the reliable management of signal??

You should proceed as follows:

for SIGPIPE: you usually want to set to ignore SIGPIPE. Advantage: you will be synchronously informed in the send() function if a SIGPIPE is caught (return -1, and errno is set to EPIPE). No need to mess up with a signal handler.
for SIGTERM, set simply a signal handler with sigaction()

This simply looks like this:

Code:

struct sigaction act;

// ignore SIGPIPE
act.sa_handler=SIG_IGN;
sigemptyset(&act.sa_mask);
act.sa_flags=0;
sigaction(SIGPIPE, &act, NULL); 

// set my handler for SIGTERM
act.sa_handler=catcher;
sigemptyset(&act.sa_mask);
act.sa_flags=0;
sigaction(SIGTERM, &act, NULL);

In particular, don't use sigprocmask. You would block the signal SIGTERM and SIGPIPE, preventing effectively your handlers to run!

HTH,
Lo�c.

Loic Domaigne

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LEARN ABOUT SUNOS

siginterrupt

siginterrupt(3C)					   Standard C Library Functions 					  siginterrupt(3C)

NAME

       siginterrupt - allow signals to interrupt functions

SYNOPSIS

       #include <signal.h>

       int siginterrupt(int sig, int flag);

DESCRIPTION

       The  siginterrupt()  function  changes  the restart behavior when a function is interrupted by the specified signal. The function siginter-
       rupt(sig, flag) has an effect as if implemented as:

       siginterrupt(int sig, int flag) {
	    int ret;
	    struct sigaction act;
	    (void) sigaction(sig, NULL, &act);
	    if (flag)
		 act.sa_flags &=  SA_RESTART;
	    else
		 act.sa_flags |= SA_RESTART;
	    ret = sigaction(sig, &act, NULL);
	    return ret;
       }

RETURN VALUES

       Upon successful completion, siginterrupt() returns 0. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

       The siginterrupt() function will fail if:

       EINVAL	       The sig argument is not a valid signal number.

USAGE

       The siginterrupt() function supports programs written to historical system interfaces. A standard-conforming application, when being  writ-
       ten or rewritten, should use sigaction(2) with the SA_RESTART flag instead of siginterrupt().

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sigaction(2), signal.h(3HEAD), attributes(5), standards(5)

SunOS 5.10							    1 Sep 2003							  siginterrupt(3C)