叉树C程序

Question

I'm trying to create fork tree diagram, but still with no success. Here is my code:

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

void procStatus(int level) {
   printf("L%d: PID[%d] (PPID[%d])\n", level, getpid(), getppid());
   fflush(NULL);
}

void levelFork(int *level) {
   if (fork() == 0)
      (*level)++;
   wait(NULL);
}

void main() {
   int level = 0;
   procStatus(level);
   levelFork(&level);
   procStatus(level);
}

I want to create like this picture below:

And this is output look like:

Any help would be appreciated.

Answer 1

Code will be like this, you should fork two child for every new child process until reached target depth level ,after forking two child,parent process must exit system, only new child process should create new processes ,

you can discard parent processes by looking childpid(return value of fork)

  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <sys/wait.h>
  #include <math.h>

int main(int argc, char *argv[])
{

pid_t childpid;
int i, n;
if (argc != 2) {
    fprintf(stderr, "Usage: %s n\n", argv[0]); return 1;
}
n = atoi(argv[1]);
childpid=-1;
for (i = 1; i <= n; i++){

    int b;
    for(b=0;b<2;b++)
    {
        childpid=fork();
        if (childpid <= 0) break;

    }
    if (childpid > 0) break;

}
while(wait(NULL) > 0) ; /* wait for all of your children */


fprintf(stderr, "i:%d process ID:%ld parent ID:%ld child ID:%ld\n",i, (long)getpid(), (long)getppid(), (long)childpid);
return 0;
}

output of code is this

└──╼ $./fork.o 2
i:3 process ID:23913 parent ID:23911 child ID:0
i:3 process ID:23915 parent ID:23911 child ID:0
i:3 process ID:23914 parent ID:23912 child ID:0
i:3 process ID:23916 parent ID:23912 child ID:0
i:2 process ID:23911 parent ID:23910 child ID:23915
i:2 process ID:23912 parent ID:23910 child ID:23916
i:1 process ID:23910 parent ID:23277 child ID:23912

Answer 2

You need a way of specifying the max depth and then using that to fork new processes. Once you are done with the forking you can start the printing. The snippet below should work

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

void procStatus(int level) {
   printf("L%d: PID[%d] (PPID[%d])\n", level, getpid(), getppid());
   fflush(NULL);
}

void levelFork(int *level,int maxlevel) {
  int locallevel= *level;
   while(locallevel!=maxlevel){
      int pid = fork();
      if (pid  == 0){
         (*level)++; // childs level is higher
         levelFork(level,maxlevel);
         return;
      }
     locallevel++;
     wait(NULL);
   }
}

void main() {
        int level = 0;
        int maxlevel=3;

        levelFork(&level,maxlevel);
        procStatus(level);
}