We always want to classify unknown events. When it happens, passing a piece of code as a parameter to other methods is the easiest way to do it, which means we want to work with the code like we do with the data.
A new process object can be created by proc:
ruby> Quux = proc {
| print "Quuxquuxquux!!! \ n "
| }
#<proc:0x4017357c>
Now Quux points to an object, and like any other object, it has behavior that can be invoked. In particular, we can execute it using the call method:
Ruby> Quux.call
Quuxquuxquux!!!
Nil
So can quux be used as a parameter to a method?
Ruby> def run (p)
| Print "About to call a procedure...\n"
| P.call
| Print "there:finished.\n"
| End
Nil
Ruby> Run Quux
About to call a procedure ...
Quuxquuxquux!!!
There:finished.
Nil
The trap method allows us to make our own choices for any system signal.
ruby> Inthandler = proc{print "^c was pressed.\n"}
#<proc:0x401730a4>
Ruby> trap "SIGINT", Inthandler
#<proc:0x401735e0>
In general, typing ^c will cause the interpreter to exit. But now a message is printed and the interpreter continues to execute, so you won't lose the job you're working on. (You don't stay in the interpreter forever, you can still exit with exit or press ^d)
The last thing to note before we start the next section is that you don't have to name a process object before you bind a process object to a signal. An equivalent anonymous (anonymous) process object like this
Ruby> trap "SIGINT", proc{print "^c was pressed.\n"}
Nil
or more briefly,
Ruby> trap "SIGINT", ' print ' ^c was pressed.\n '
Nil
This shorthand provides you with a convenient and readable way to write a small anonymous process.
