Thread: Pointers or fork?

  1. #1
    Registered User
    Join Date
    Mar 2009

    Pointers or fork?


    I don't know where is the problem in my code, since in the debbuger I cannot see what goes on with the child process. May someone help.

    void addJob(int pid, int status){
        jobs* temp = job;
        if (temp == NULL){
        	temp = malloc(sizeof(jobs*));
        	job = temp;
        	while (temp != NULL) temp = temp->next;
        	temp = malloc(sizeof(jobs*));
        temp->pid = pid;
        temp->status = status; /* foreground */
        if (pid == 0){
        	pid_t npid = getpid();
        	printf("If successful, the process ID will be %d.\n",npid); fflush(stdout); /* I know it reaches here */
        	addJob(npid, (bg)? 0:1);
        	if (execvp(*args, args) == -1){ perror("executing command\n"); exit(1);}
    where job is a global variable.
    May I know why the statement is not executed, or is so but not adding to the list? Is it an issue of shared memory amongst the processes? I've put jobs as a static variable in a header file and imported it but I still get no difference.

  2. #2
    Officially An Architect brewbuck's Avatar
    Join Date
    Mar 2007
    Portland, OR
    forked processes do NOT share memory.

    You need to get the child pid in the PARENT (it is the return value of fork() ) and insert it into the job list in the PARENT.

    EDIT: addJob() looks all wrong, too, but that's a different issue.
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);

  3. #3
    Registered User
    Join Date
    Mar 2009
    I know other methods to add an element to the end of a list, but just for my better understanding, may you tell me what's wrong such that I fix this itself?

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