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Full Discussion: pipe help
Top Forums Programming pipe help Post 16063 by Perderabo on Monday 25th of February 2002 08:16:35 AM
Old 02-25-2002
Well, here is a quickie example of a pipe:
Code:
#include <stdio.h>   
#include <unistd.h>

void main()
{
        int pid, pipefd[2], parentpid, childpid;

        parentpid=getpid();
        pipe(pipefd);

        if (pid=fork()) {
                printf("I am the parent process and my pid is %d\n", getpid());
                printf("My child process has a pid of %d\n", pid);
                read(pipefd[0], (char *) &childpid, sizeof(childpid));
                printf("My child process sent me %d\n", childpid);
        } else {
                childpid=getpid();
                printf("I am the child and my pid is %d\n", childpid);
                write(pipefd[1], (char *) &childpid, sizeof(childpid));
                exit(0);
        }

        printf("I am still the parent process and my pid is %d\n", getpid());
        exit(0);
}

A broken pipe means that you are writing onto a pipe that has been closed by the other end.
 

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getpid(2)							   System Calls 							 getpid(2)

NAME
getpid, getpgrp, getppid, getpgid - get process, process group, and parent process IDs SYNOPSIS
#include <unistd.h> pid_t getpid(void); pid_t getpgrp(void); pid_t getppid(void); pid_t getpgid(pid_t pid); DESCRIPTION
The getpid() function returns the process ID of the calling process. The getpgrp() function returns the process group ID of the calling process. The getppid() function returns the parent process ID of the calling process. The getpgid() function returns the process group ID of the process whose process ID is equal to pid, or the process group ID of the calling process, if pid is equal to 0. RETURN VALUES
Upon successful completion, these functions return the process group ID. Otherwise, getpgid() returns (pid_t)-1 and sets errno to indicate the error. ERRORS
The getpgid() function will fail if: EPERM The process whose process ID is equal to pid is not in the same session as the calling process, and the implementation does not allow access to the process group ID of that process from the calling process. ESRCH There is no process with a process ID equal to pid. The getpgid() function may fail if: EINVAL The value of the pid argument is invalid. 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), fork(2), getsid(2), setpgid(2), setpgrp(2), setsid(2), signal(3C), attributes(5), standards(5) SunOS 5.10 28 Dec 1996 getpid(2)
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