Computer Science 322
Operating Systems

Lecture 17: Unix Systems Programming
Date: Wednesday, March 26, 2008

Quote: UNIX system calls, reading about those can be about as interesting as reading the phone book... - George Williams, 3/12/91

Announcements
- Reminder: round robin CPU scheduler simulation grading - come see me to demonstrate your code
Unix Systems Programming
- Process management
  - PID queries: getpid(2), getppid(2)
  - Process creation: fork(2), vfork(2)
  - Process termination: exit(3), _exit(2)
  - Parent notification: wait(2), waitpid(2)
- Starting new programs - exec system calls
  - To fork(2) anything but a copy of yourself...
  - execl(3), execv(3), execlp(3), execvp(3)
  - varags vs. arrays, search path or not?
- Signals
  - Interprocess communication mechanism
  - kill -l to list signal types
  - kill -SIGNAL pid to send a signal to a process
  - Every process has signal handlers - react to signals sent to the process.
  - A default signal handler is attached when a process is created
  - signal(3) replaces signal handler
    - custom function
    - SIG_IGN, SIG_DFL
  - setitimer(2) to set alarm to deliver SIGALRM
  - kill(2) sends signals from a program
- Low-level file operations
  - C stdio routines (printf and friends) are fairly high level
  - low-level operations: open(2), close(2), read(2), write(2)
  - work with file descriptors

No new lecture assignment for Friday.

Our next topic is deadlock, covered in SG&G Chapter 7.