OS Services
Or everything you ever wanted to know about UNIX but were too afraid to ask
Vital Statistics
- Name
- Dave Jones
- @waveform80
- GitHub
- github.com/waveform80
What's UNIX ever done for us?
- Well, there's the process scheduling
- and the file-system
- oh, and the sockets, Dave
- and the privilege separation
- and don't forget the memory isolation
Alright!
But aside from the process scheduling, the file-system, the sockets, the privilege separation, and the memory isolation … what has UNIX ever done for us?
Part 1
Processes
Most functions
- Take n parameters
- Perform some work
- Return a value
Weird functions
sys.exit(1)- Takes 1 parameter
- Doesn't return (as far as your program is concerned)
Weirder functions
os.fork()- Takes no parameters
- Returns twice?!
Demo
Part 2
The File System
Atomic operations
- Exclusive file creation
- File renaming (within FS)
- File linking
Demo
What is a file?!
So what's a handle?
The name's expendable?
In fact totally distinct!
Back where we started
So the link thing …
Part 3
mmap
Virtual memory
- Every process sees the same address space
- Memory pages can be backed by nothing!
- Memory pages can be backed by RAM
- Memory pages can be backed by files
Demo
Part 4
Pipes, FIFOs, Sockets, etc.
No, not those sockets
- UNIX sockets, like files but …
- FIFOs, like files but …
Demo
Vital Statistics
- Name
- Dave Jones
- Occupation
- File Whisperer
- @waveform80
- GitHub
- github.com/waveform80
Available Now!
from your nearest web-server
www.waveform.org.uk/presentations/ipc/Thank You
Questions? Pub!