1. Andy Wang Operating Systems COP 4610 / CGS 5765
Project 1 Hints
Andy Wang
Operating Systems
COP 4610 / CGS 5765

2. Overall Parsing chdir() is a system call
Use calloc() instead of malloc()
Use multiple passes to simply parsing
One pass to create an array of string tokens
One pass for input redirection
One pass for output redirection
chdir() is a system call

3. Foreground Execution
fork()
Shell
Shell
waitpid(pid, &status, 0)

4. Foreground Execution fork() Shell Shell execvp(bin_path, argv)
waitpid(pid, &status, 0)

5. Foreground Execution
fork()
Shell
Shell
waitpid(pid, &status, 0)

6. Background Execution
fork()
Shell
Shell
waitpid(-1, &status,
WNOHANG)

7. Background Execution fork() Shell Shell execvp(bin_path, argv)
waitpid(-1, &status,
WNOHANG)

8. Background Execution
fork()
Shell
Shell
waitpid(-1, &status,
WNOHANG)

9. Input Redirection shell file descriptors 0 stdin 1 stdout 2 stderr
fork()
file descriptors
0 stdin
1 stdout
2 stderr
shell

10. Input Redirection open(input_file, O_RDONLY) file descriptors 0 stdin
1 stdout
2 stderr
file descriptors
0 stdin
1 stdout
2 stderr
shell
shell

11. Input Redirection open(input_file, O_RDONLY) file descriptors 0 stdin
1 stdout
2 stderr
file descriptors
0 stdin
1 stdout
2 stderr
3 input_file
shell
shell

12. Input Redirection close(0) file descriptors 0 stdin 1 stdout 2 stderr
3 input_file
shell
shell

13. Input Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr
1 stdout
2 stderr
3 input_file
shell
shell

14. Input Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr
0 input_file
1 stdout
2 stderr
3 input_file
shell
shell

15. Input Redirection close(3) file descriptors 0 stdin 1 stdout 2 stderr
0 input_file
1 stdout
2 stderr
3 input_file
shell
shell

16. Output Redirection shell file descriptors 0 stdin 1 stdout 2 stderr
fork()
file descriptors
0 stdin
1 stdout
2 stderr
shell

17. Output Redirection open(output_file, O_RDWR | O_CREAT | O_TRUC)
file descriptors
0 stdin
1 stdout
2 stderr
file descriptors
0 stdin
1 stdout
2 stderr
shell
shell

18. Output Redirection open(output_file, O_RDWR | O_CREAT | O_TRUC)
file descriptors
0 stdin
1 stdout
2 stderr
file descriptors
0 stdin
1 stdout
2 stderr
3 output_file
shell
shell

19. Output Redirection file descriptors 0 stdin 1 stdout 2 stderr
3 output_file
shell
close(1)
shell

20. Output Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr
3 output_file
shell
shell

21. Output Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr
1 output_file
2 stderr
3 output_file
shell
shell

22. Output Redirection close(3) file descriptors 0 stdin 1 stdout 2 stderr
1 output_file
2 stderr
3 output_file
shell
shell

23. Pipe int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin
1 stdout
2 stderr
shell

24. Pipe int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell

25. Pipe shell file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0]
int p1_to_p2[2];
pipe(p1_to_p2);
fork()
int p1_to_p2[2];
pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell

26. Pipe shell file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0]
int p1_to_p2[2];
pipe(p1_to_p2);
fork()
int p1_to_p2[2];
pipe(p1_to_p2);
int p1_to_p2[2];
pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell
shell

27. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell
shell
shell

28. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin 1
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
dup(4)
shell
shell
shell

29. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
dup(4)
shell
shell
shell

30. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell
shell
shell

31. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell
shell
shell

32. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell
shell
shell

33. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell
shell
shell

34. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
dup(3)
shell
shell
shell

35. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 p1_to_p2[0]
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
dup(3)
shell
shell
shell

36. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 p1_to_p2[0]
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
shell
shell
shell

37. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 p1_to_p2[0]
1 stdout
2 stderr
shell
shell
shell

38. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 p1_to_p2[0]
1 stdout
2 stderr
execvp(bin_path,
argv)
shell
shell
shell

39. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
3 p1_to_p2[0]
4 p1_to_p2[1]
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 p1_to_p2[0]
1 stdout
2 stderr
execvp(bin_path,
argv)
shell
shell
shell

40. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 p1_to_p2[0]
1 stdout
2 stderr
execvp(bin_path,
argv)
shell
shell
shell

41. Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2);
file descriptors
0 stdin
1 stdout
2 stderr
waitpid(…)
file descriptors
0 stdin
1 p1_to_p2[1]
2 stderr
execvp(bin_path,
argv)
file descriptors
0 p1_to_p2[0]
1 stdout
2 stderr
execvp(bin_path,
argv)
shell
shell
shell