Operating Systems 2019W Lecture 6

Video

Video from the lecture given on January 23, 2019 is now available.

Notes

Topics for today

• environment variables
• signal handlers
• I/O redirection

In Class

Lecture 6
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Topics
 - signal handlers
 - I/O redirection
 - environment variables & command line arguments


Key ideas for signals
* processes can register signal handler functions for specific signals
* When the kernel delivers a signal to a process, it runs the specified handler
* The C library defines default handlers for all signals (except STOP and KILL)
* When a process gets a signal, current execution is interrupted and the handler
  is invoked.  When the handler terminates, the process continues where it was

* If the process was blocked on a system call, the system call is interrupted
  and the handler is run.
* The standard library can do different things with interrupted system calls