Project created for passing Operating Systems subject in
High School of Information Technology


Example usages
--------------

Without bootstrap program
=========================

In separate terminals enter:
$ ./bin/process1
$ ./bin/process2
$ ./bin/process3

After that in terminal with process1 running enter some characters followed by
new line (ENTER).

- Process1 displays information about data buffer and how many bytes has been
  sent to process2.
- Process2 displays information about received bytes, prints to stderr info
  about number of characters in buffer, and sent this value to process3.
- Process3 displays information about number of entered characters.

With bootstrap program
======================

In terminal, go to the ./bin directory (where compiled programs resides).
Execute:
$ ./bootstrap

After that there should be shown info about spawning new processess.
You can now pass to the standard input of the first spawned process data, .e.g:
$ echo "qwertyuiop" > /proc/(process 0 pid)/fd/3

If process creation was completed without errors, you should see following output:
[process2] Fetched: 11 bytes
[process2] Calculated: 10 characters. Sending...
[process3] Fetched: 4 bytes
[process3] Process2 send: 10

Signalling
==========

After bootstrapping processes, you can send them signals.
Processes registers custom handlers for following ones:
- SIGUSR1 (User defined signal 1) - used for internal purposes. Signal must be
  sent in pair with message queue.
- SIGTERM (Terminated) - additionaly to standard behaviour, this signal allows
  releasing aquired resources and notify other processes using SIGUSR1 to do the
  same.
- SIGTSTP (Stopped) - additionaly to standard behaviour, this signal allows
  holding aquired resources (closes pipes for example), and notify other
  processes using SIGUSR1 to do the same.
- SIGCONT (Continued) - aditionaly to standard behaviour, this signal allows
  resume process working by opening closed pipes, and notify other processes
  using SIGUSR1 to do the same.