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Old 03-21-2009, 04:56 AM   #1
karana
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Registered: Aug 2005
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linux C exec fork


i have a linux pthread ...I am calling vfork and then exec another program .....But the child becomes zombie ...? please find the pseodo code inside pthread

//****************inside a pthread

if(vfork()==0)
{
exec ("/home/rat/print");
_exit(0);
}

//*************end
 
Old 03-21-2009, 07:48 AM   #2
tronayne
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Not vfork() specifically, but a how-to for fork-excel you may find useful.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>

int     main    (void)
{
        char    line [BUFSIZ];
        int     fifo [2], proc, n;

        (void) pipe (fifo);
        if ((proc = fork ()) == -1) {
                (void) fprintf (stderr, "can't fork\n");
                exit (errno);
        }
        if (proc == 0) {        /* child        */
                /*
                 *      close the standard input and
                 *      dup write end of pipe onto it
                */
                (void) close (1);
                (void) dup (fifo [1]);
                /*      run pwd with standard output attached to pipe   */
                (void) execl ("/bin/pwd", "pwd", NULL);
                /*      execl shouldn't return                          */
                (void) fprintf (stderr, "cannot execl pwd\n");
                exit (errno);
        }
        /*      parent: read from pipe                                  */
        n = read (fifo [0], line, BUFSIZ);
        line [n] = '\0';
        (void) fprintf (stdout, "current directory = %s", line);
        exit (EXIT_SUCCESS);
}
[EDIT]
Well, I thought about it a little more and here's a slightly simpler example; it prompts for a command, forks-and-exec's the command (until you just hit the carriage return at the prompt):
Code:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <wait.h>
#include <sys/types.h>

int     main    (void)
{
        char    line [BUFSIZ];
        int     process;

        for ( ; ; ) {
                (void) fprintf (stderr, "cmd: ");
                if (gets (line) == (char *) NULL)
                        exit (EXIT_FAILURE);
                /*      create new process      */
                if ((process = fork ()) > 0)
                        (void) wait ((int *) NULL);
                else if (process == 0) {        /* child        */
                        /*      execute program                 */
                        (void) execlp (line, line, NULL);
                        /*      some problem if exec returns    */
                        (void) fprintf (stderr, "can't execute %s\n", line);
                        exit (errno);
                } else if (process == -1) {     /* can't create */
                        (void) fprintf (stderr, "can't fork\n");
                        exit (errno);
                }
        }
}
For, pretty much, any fork-and-exec this describes what you need to do so you don't wind up with zombies and the like. Check the man pages for the exec functions and adjust the arguments accordingly.

Hope this helps some.

Last edited by tronayne; 03-22-2009 at 08:40 AM.
 
  


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