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  1. /*    main program illustrating the UNIX fork() system call. 
  2. Compile using cc -o main main.c
  3. */
  4. #include <stdio.h>
  5. #include <stdio.h>
  6. #include <sys/types.h>
  7. #include <unistd.h>
  8.  
  9. int main() {
  10.     pid_t pid1 = 0, pid2 = 0, pid3 = 0, pid4 = 0, pid5 = 0, pid6 = 0;
  11.  
  12.     pid1 = fork();
  13.     printf("pid1 has been executed!");
  14.     if (pid1 == 0) {  // Child process
  15.         pid2 = fork();
  16.         printf("A");
  17.         printf("pid2 has been executed!");
  18.         printf("Process %d created, Parent: %d\n", getpid(), getppid());
  19.     } else {  // Parent process executes execvp
  20.         char *args[] = {"/bin/ls", NULL};
  21.         execvp(args[0], args);
  22.     }
  23.  
  24.     printf("Process %d created, Parent: %d\n", getpid(), getppid());
  25.     printf("B");
  26.     pid3 = fork();
  27.     if (pid4 != 0) {  // Parent process
  28.     	printf("C");
  29.         printf("Process %d created, Parent: %d\n", getpid(), getppid());
  30.         char *args[] = {"/bin/ls", NULL};
  31.         execvp(args[0], args);
  32.     } else {  // Child process
  33.         if (pid1 != 0) {  // If this is not the first child
  34.             pid5 = fork();
  35.             printf("Process %d created, Parent: %d\n", getpid(), getppid());
  36.             char *args[] = {"/bin/ls", NULL};
  37.             execvp(args[0], args);
  38.             printf("D");
  39.         }
  40.     }
  41.  
  42.     if (pid2 > 0) {  // Only for the original parent process
  43.         pid6 = fork();
  44.         printf("E");
  45.         printf("Process %d created, Parent: %d\n", getpid(), getppid());
  46.     } else {  // pid2 == 0 case
  47.     	printf("F");
  48.         printf("Process %d created, Parent: %d\n", getpid(), getppid());
  49.         char *args[] = {"/bin/ls", NULL};
  50.         execvp(args[0], args);
  51.     }
  52.  
  53.     printf("G");
  54.  
  55.     printf("Process %d created, Parent: %d\n", getpid(), getppid());
  56.  
  57.     return 0;
  58. }
Success #stdin #stdout 0.01s 5284KB
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stdin
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Standard input is empty
stdout
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prog
pid1 has been executed!Apid2 has been executed!Process 3502448 created, Parent: 1
Process 3502448 created, Parent: 1
BEProcess 3502448 created, Parent: 1
GProcess 3502448 created, Parent: 1
pid1 has been executed!Apid2 has been executed!Process 3502448 created, Parent: 1
Process 3502448 created, Parent: 1
BEProcess 3502451 created, Parent: 1
GProcess 3502451 created, Parent: 1
https://ideone.com/6w5dVY
language:
C (gcc 8.3)
created:
10 days ago
visibility:
public

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