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Project #1: Week 3

Project #1: Week 3. Principles of Operating Systems (LAB) COP 4610/CGS 5765. Overview. Pipelining Processes fork() execv () Environment Variables. Clarification in Description. cd "$OLDPWD" && pwd Do not have to implement ‘ && ’

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Project #1: Week 3

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  1. Project #1:Week 3 Principles of Operating Systems (LAB) COP 4610/CGS 5765

  2. Overview • Pipelining • Processes • fork() • execv() • Environment Variables

  3. Clarification in Description • cd "$OLDPWD" && pwd • Do not have to implement ‘&&’ • OLDPWD can be stored as an environment variable, but it is not necessary since there is not requirement to allow user to display them

  4. pipe() • Interprocess data channel #include <unistd.h> intpipe(intfildes[2]); [1] - write [0] - read http://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html

  5. Pipe • ls | grep • fork() x2 • create a pipe • redirect fd=1 of process to be ls to write end of pipe • redirect fd = 0 of process to be grep to read end of pipe • execvgrep and ls binaries

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  25. Process State Diagram exit, kill start zombie (terminated) event occurs ready (competing for execution time) blocked (waiting) wait*() end of life (no allocated resources) interrupt scheduler dispatch running (executing) event wait

  26. fork() • How does the forked process differ? • http://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html

  27. Process State Data/Code Stack Directly accessible Registers File descriptor Table Entries Indirectly accessible (e.g., OS call) . . . Scheduling Information

  28. execv() Executable File Data/Code copy Code Data Stack Registers initialize File descriptor Table Entries . . . Scheduling Information

  29. Environment Variables extern char **environ; • pointer to an array of strings • Required not to directly modify the pointers to which environ points

  30. Parsing Strings • strtok_r() • See code example on website

  31. Process Groups • See example

  32. Questions

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