Thread: system command output.

  1. #1
    Registered User
    Join Date
    Aug 2002

    system command output.

    Hello. This is my first post here and I just started learning C, so please do not be too harsh in responces.

    I was wondering how you can get system() or another function to call a system command and return the output not to STDOUT, but to a variable instead. This is so I may parse the output myself and print it how I wish to the user.

    Thanks to anyone who provides valid info.

  2. #2
    Registered User moi's Avatar
    Join Date
    Jul 2002
    FILE *foo_output;

    system ("foo.exe > foo_response");

    foo_output = fopen ("foo_response", "rt");

    // something like that?
    hello, internet!

  3. #3
    Banned Troll_King's Avatar
    Join Date
    Oct 2001
    What operating system are you using?

    If you are using Linux than the shell is powerful. Write a script.

    If you are using Microsoft and VC++6 than you can use the system(" ..."); call in your program. You can also pass command line arguments to the program.

    Use redirection:

    ls /home/User > file.out
    Last edited by Troll_King; 08-21-2002 at 07:28 AM.

  4. #4
    End Of Line Hammer's Avatar
    Join Date
    Apr 2002
    Another approach is to use a pipe, if you have those functions available to you (they're non-standard). Be careful with this method though, sometimes the pipe will get stuck if things don't go right. Use with caution!
    /* This was written under Borland 5.5 */
    #include <stdio.h>
    #include <stdlib.h>
    int main(void)
        char buf[BUFSIZ];
        FILE *fp;
        if ((fp = _popen("ping", "r")) == NULL)
            perror("pipe failure");
            return (EXIT_FAILURE);
        while (fgets(buf, sizeof(buf), fp))
            printf ("OUTPUT: %s\n", buf);
        return (EXIT_SUCCESS);
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

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