Operating Systems 2021F Lecture 11

Notes

Lecture 11
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Midterm review
 - Assignment 2 solutions
 - Assignment 1 solutions
 - key concepts

Class will end at 11
 - I have to run to the airport!

Most system calls (that would be used in a regular program) have a corresponding library call (that is a thin wrapper around the system call)
 - so if you see it in strace there's probably a way of calling it

C library functions are pretty cross-platform
 - but they are very closely associated with UNIX

Remember that printf goes to standard out
  equivalent to fprint(stdout, ...)

So fprint(stderr, ...) is going to a different place
 - just normally in a terminal 1 and 2 are going to the terminal
   (standard out and standard error)

I don't expect your solutions to be identical to mine
 - you just need to answer the question in a way that shows you understand the key concepts
 - there are multiple valid solutions to many of the questions,
   but they differ in implementation strategy, not in an
   understanding of what is going on

Kill vs signal
 - kill is for sending signals
 - signal is for receiving signals
    - not quite standardized, so nowadays
      you're supposed to use sigaction, not signal

The C library defines standard signal handlers for all signals
 - most just terminate the process

Submissions for the midterm will be exactly like the assignments
 - submit a text file
 - auto grading isn't possible, as it will almost all be short answer

Officially 80 minutes
 - don't submit multiple times
 - if there are problems, just email your answers to me or
   send them via Teams

If you did the tutorials correctly, the assignments should be pretty straightforward
 - so if you found the assignment to be very hard,
   rethink how you do tutorials

Questions during the midterm
 - teams
 - open zoom (office hours)
 - info will be on midterm PDF

Remember redirecting standard error for a command doesn't change standard error for the main shell