Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

direct system() output to socket

Posted on 2000-03-01
3
Medium Priority
?
300 Views
Last Modified: 2011-09-20
We have a client app that connects to a server.  The server executes system() command(s), directing the output to a file.  The system command may be calling a batch.  We then read the file and send the contents back to the client.  Ideally the ouput would be send to the client as it happens, instead of all at the end.  Is is possible to direct the ouput to an open socket?  I guess we could fork(), call system(), and then poll the file, but seems like there should be an easier way.
Thank You.
0
Comment
Question by:marvinm
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 1

Accepted Solution

by:
sereda earned 800 total points
ID: 2573733
Yes, surely. There are many ways for IPC.
You can use pipes for your example.
Simple example code:

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

int main () {
    int fd[2];
    int pid;
    char buf[1000];
    int i, d;

    pipe (fd);
    pid = fork();

    if (pid == 0) {
        // child
        close (fd[0]);
        // now - here is the catch:
        // we close stdout and make a dup of fd[1] handle, which creates minimal descriptor to our pipe, in fact - 1.
        close (1);
        dup (fd[1]);
        // after this line all stdout is going into pipe
        system ("echo HELLOWORLD");
        exit(0);
    }
    // parent
    close(fd[1]);

    // here is a ugly pipe reading
    // but you can perform any other mechanism
    // all output might be read from fd[0]
    for (i = 0; i < 100; i++) {
      usleep (10000);
      bzero (buf, 1000);
      if (read (fd[0], buf, 1000) > 0)
        printf ("received: [%s]\n", buf);
    }
    exit (0);
}


Hope this helps.
0
 
LVL 1

Expert Comment

by:sereda
ID: 2580166
Hi,
in fact if you don't need stdout in main process you can simply put that:

redirectoutput (int socket_handle) {
  close (1);
  dup (socket_handle);
  system ("echo BBB");
}

Pretty simple, heh?
0
 
LVL 1

Author Comment

by:marvinm
ID: 2617433
Thank You
0

Featured Post

Tech or Treat!

Submit an article about your scariest tech experience—and the solution—and you’ll be automatically entered to win one of 4 fantastic tech gadgets.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Installing FreeBSD… FreeBSD is a darling of an operating system. The stability and usability make it a clear choice for servers and desktops (for the cunning). Savvy?  The Ports collection makes available every popular FOSS application and packag…
I have been running these systems for a few years now and I am just very happy with them.   I just wanted to share the manual that I have created for upgrades and other things.  Oooh yes! FreeBSD makes me happy (as a server), no maintenance and I al…
Learn how to find files with the shell using the find and locate commands. Use locate to find a needle in a haystack.: With locate, check if the file still exists.: Use find to get the actual location of the file.:
This video shows how to set up a shell script to accept a positional parameter when called, pass that to a SQL script, accept the output from the statement back and then manipulate it in the Shell.
Suggested Courses

609 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question