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using SIGCHLD

 
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# 1  
Old 02-16-2011
using SIGCHLD
I'm testing out how to use SIGCHLD and I had a question about intercepting the signal and executing an action in the signal handler.

Code:
signal(SIGCHLD,countdown);

What I'm trying to achieve is be able to printf(Hello) every second that child is set to sleep.

I'm setting sleep = 3;

so what I would like countdown to do is print Hello 3 times like so:
Quote:
Hello
Hello
Hello
Last edited by Yogesh Sawant; 02-16-2011 at 04:00 AM.. Reason: added quote tags
# 2  
Old 02-16-2011
Assuming I understand what you wrote:

SIGCHLD arrives AFTER the child process ends, not when it is created. So counting down is not going to happen while the child process is running.
I think you want this: Assume pid is a pid_t variable that is the pid of the child.
Code:
 while ( (retval=waitpid(pid, &status_value, WNOHANG)==0) )
 {
    printf("Hello\n");
    sleep(1);
 }
 /* process the result based on retval == pid or retval == -1 */
 /* next process the status_value which is the return status of the child */

 
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