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Full Discussion: Signal handling
Top Forums Programming Signal handling Post 302320138 by #moveon on Wednesday 27th of May 2009 06:54:15 AM
Old 05-27-2009
Signal handling

I am trying to write a small program where I can send signals and then ask for an action to be triggered if that signal is received. For example, here is an example where I am trying to write a programme that will say you pressed ctrl*c when someone presses ctrl+c. My questions are what you would expect from a beginner so bear with me. First, how can I get ro test the functionality of my program? My udnerstanding is you get the process ID and then through kill -signalnumber PID you will be able to send the signal? For example kill -2 2345 to send teh SIGINT to PID 2345. But mine doesn't work. First I opened a new shell then used shellname & on the terminal to get the PID, then on the terminal wrote kill -2 2345 if the PID was that for example. But I always recieve '... No such process'. Where I am getting it wrong?
Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <errno.h>
    #include <signal.h>
    void signalhandler(int sig);

    int main(void)
    {
    char s[200];
    
        (void) signal (SIGINT, signalhandler);
    
                
        if (signal(SIGINT, signalhandler) == SIG_ERR) {
            perror("signal");
            exit(1);
        }
            return 0;
    }
    
            void signalhandler(int sig)
    {
        printf("You pressed CTRL+C!\n");
    }

 

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kill(1) 						      General Commands Manual							   kill(1)

Name
       kill - send a signal to a process

Syntax
       kill [-sig] processid...
       kill -l

Description
       The command sends the TERM (terminate, 15) signal to the specified processes.  If a signal name or number preceded by `-' is given as first
       argument, that signal is sent instead of terminate.  For further information, see

       The terminate signal kills processes that do not catch the signal; `kill -9 ...' is a sure kill, as the KILL (9) signal cannot  be  caught.
       By convention, if process number 0 is specified, all members in the process group (that is, processes resulting from the current login) are
       signaled.  This works only if you use and not if you use To kill a process it must either belong to you or you must be superuser.

       The process number of an asynchronous process started with `&' is reported by the shell.  Process numbers can also be  found  by  using	It
       allows job specifiers ``%...''  so process ID's are not as often used as arguments.  See for details.

Options
       -l   Lists  signal  names.  The signal names are listed by `kill -l', and are as given in /usr/include/signal.h, stripped of the common SIG
	    prefix.

See Also
       csh(1), ps(1), kill(2), sigvec(2)

																	   kill(1)
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