Re: signals ??

["Prateek Gera" <prateekg@xxxxxxxxxxxxxxx>]

nitin mahajan <nitin.mahajan@xxxxxxx> on 18/05/2000 04:41:46 PM

Please respond to linux-india-programmers@xxxxxxxxxxxxxxxxxxxxx

To:   linux-india-programmers@xxxxxxxxxxxxxxxxxxxxx
cc:    (bcc: Prateek Gera/TMs/TCSDELHI/TCS)
Subject:  [LIP] signals ??




Hello ,

Well i seem to be having problem passing signals betwen processe's in Linux
,
can some one tell me
where am i bingling up .. i say had installed a signal handler for a signal
(infact tried all listed in Steven's) in a child process and when i send
this
signal from the parent of this child it was getting lost (i mean handler
wasn't being called )
any comments ??
then is static global variables the way to pass reliably the information
b/w
processe's ??

i am attaching a sample code saying what i was observing .. simple while
(1)
loops in both parent and child with parent terminating when user presses
control-C and child is supposed to when it gets the SIGUSR1 from parent .

# include <sys/types.h>
# include <sys/wait.h>
# include <stdio.h>
# include <unistd.h>
# include <signal.h>
static int int_occured =0 ;
static int int_occured2 =0;
void handler(int i);
void usr1handler(int i);

void handler(int i)
{
 printf("OK I AM INSIDE THE HANDLER NOW  /n");
                    /* this wasn't printed so we cannot print from inside
the handler?? */

 sleep(2);
 int_occured=1;
 kill(0,SIGUSR1);

}

void usr1handler(int i)
{
     printf("USR1 HAS BEEN THERE INTO ACTION NOW"); // basically it's to be
used
to set int_ocured2 so that child also gets out of while loop //
     int_occured2=1;
        sleep(10);

}


main ()

{
     int chpid ;
     setpgrp();
     signal(SIGINT,handler);
     signal(SIGUSR1,SIG_IGN);

          while (!int_occured)
     {
          printf("not recvd. signal as of now !!, %d", getpid());
     }
     if ((chpid = fork()) ==0)
     {
          signal(SIGINT,SIG_DFL);
          signal(SIGUSR1,usr1handler);
          printf("ok this is the good ol's child and VALUE OF
INT!,%d",int_occured);


          while(!(int_occured2))
          {
               printf("nahi main nahin maanonga  :)),%d , %d",
int_occured,getpid());

          }
          printf("I AM INSIDE THE CHILD NOW");
     }
     else signal(SIGUSR1,SIG_IGN);

     printf("ok out of while loop ! "); // but never printed //
     exit(0);

}


With much modesty please point to this fella where i am goin wrong :(

Luv,
Nitin

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