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Full Discussion: Message passing from child to parent using pipes
Special Forums IP Networking Message passing from child to parent using pipes Post 302857989 by abhi1988sri on Friday 27th of September 2013 11:42:17 PM
Old 09-28-2013
Message passing from child to parent using pipes
Hi,

I am trying my hand in networking programming in C, and got stuck in piping.

I was following some tutorial and did the forking like :

Code:
while (1) 
    {
        newsockfd = accept(sockfd, 
                (struct sockaddr *) &cli_addr, &clilen);
        if (newsockfd < 0)
        {
            perror("ERROR on accept");
            exit(1);
        }
        /* Create child process */
        pid = fork();
        if (pid < 0)
        {
            perror("ERROR on fork");
	    exit(1);
        }
        if (pid == 0)  
        {
            /* This is the client process */
            close(sockfd);
            doprocessing(newsockfd);
            exit(0);
        }
        else
        {
            close(newsockfd);
        }
    } /* end of while */

I want to have:

The client forks off a child. After the child is forked off, the parent process enters a second loop in which it continually reads and prints out status messages received from the child via a half-duplex pipe.
How to do the thing in bold?

Apologies , if it is a lame question..but how do we do that or some reference of the same would help me..


Regards

Abhinav
 

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LEARN ABOUT SUNOS

setpgid

setpgid(2)							   System Calls 							setpgid(2)

NAME

       setpgid - set process group ID

SYNOPSIS

       #include <sys/types.h>
       #include <unistd.h>

       int setpgid(pid_t pid, pid_t pgid);

DESCRIPTION

       The setpgid() function sets the process group ID of the process with ID pid to pgid.

       If pgid is equal to pid, the process becomes a process group leader. See intro(2) for more information on session leaders and process group
       leaders.

       If pgid is not equal to pid, the process becomes a member of an existing process group.

       If pid is equal to 0, the process ID of the calling process is used. If pgid is equal to 0, the process specified by pid becomes a  process
       group leader.

RETURN VALUES

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

ERRORS

       The setpgid() function will fail if:

       EACCES	       The  pid  argument  matches the process ID of a child process of the calling process and the child process has successfully
		       executed  one of the exec family of functions (see exec(2)).

       EINVAL	       The pgid argument is less than (pid_t) 0 or greater than or equal to PID_MAX, or the calling process has a controlling ter-
		       minal that does not support job control.

       EPERM	       The process indicated by the pid argument is a session leader.

       EPERM	       The  pid argument matches the process ID of a child process of the calling process and the child process is not in the same
		       session as the calling process.

       EPERM	       The pgid argument does not match the process ID of the process indicated by the pid argument, and there is no process  with
		       a process group ID that matches pgid in the same session as the calling process.

       ESRCH	       The pid argument does not match the process ID of the calling process or of a child process of the calling process.

ATTRIBUTES

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

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

SEE ALSO

       intro(2), exec(2), exit(2), fork(2), getpid(2), getsid(2), attributes(5), standards(5)

SunOS 5.10							    28 Dec 1996 							setpgid(2)
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