fork(1) download 
  1. #include <stdio.h>
  2. #include <unistd.h>
  3. #include <stdlib.h>
  4. #include <sys/types.h>
  5.  
  6. int glob = 6;
  7. char buf[] = "a write to stdout\n";
  8.  
  9. void print_err(char *msg, int n) {
  10. 	write(STDOUT_FILENO, msg, n);
  11. 	exit(1);
  12. }
  13.  
  14. int main() {
  15. 	int var;
  16. 	pid_t pid;
  17.  
  18. 	var = 88;
  19.  
  20. 	if(write(STDOUT_FILENO, buf, sizeof(buf) - 1) != sizeof(buf) - 1)
  21. 		print_err("write error\n", 12);
  22.  
  23. 	printf("before fork\n");
  24.  
  25. 	if((pid = fork()) < 0)
  26. 		print_err("fork error\n", 11);
  27. 	else if(pid == 0) {
  28. 		glob++;
  29. 		var++;
  30. 		printf("pid = %d, glob = %d, var = %d\n", getpid(), glob, var);
  31. 		if((pid = fork()) < 0) print_err("fork error\n", 11);
  32. 		if(pid == 0) {
  33. 			glob++;
  34. 			var++;
  35. 			printf("pid = %d, glob = %d, var = %d\n", getpid(), glob, var);
  36. 			if((pid = fork()) < 0) print_err("fork, error\n", 11);
  37. 			if(pid == 0) {
  38. 				glob++;
  39. 			    var++;
  40. 			    printf("pid = %d, glob = %d, var = %d\n", getpid(), glob, var);
  41. 			} else {
  42. 				sleep(1);
  43. 			}
  44. 		} else {
  45. 			sleep(2);
  46. 		}
  47. 	} else {
  48. 		sleep(3);
  49. 	}
  50.  
  51. 	printf("pid = %d, glob = %d, var = %d\n", getpid(), glob, var);
  52. 	exit(0);
  53. }
  54.  
Success #stdin #stdout 0s 9424KB
comments (?)
stdin 
Standard input is empty
stdout 
a write to stdout
before fork
pid = 29334, glob = 7, var = 89
pid = 29335, glob = 8, var = 90
pid = 29336, glob = 9, var = 91
pid = 29336, glob = 9, var = 91
before fork
pid = 29334, glob = 7, var = 89
pid = 29335, glob = 8, var = 90
pid = 29335, glob = 8, var = 90
before fork
pid = 29334, glob = 7, var = 89
pid = 29334, glob = 7, var = 89
before fork
pid = 29271, glob = 6, var = 88
https://ideone.com/zyb9lW
language:
C (gcc 8.3)
created:
7 years ago
visibility:
public

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