Lesson 18

different types of interprocess communication

pipes
FIFOs
sockets
message queues
shared memory
semaphores
eventfd
file locks
mutexes
condition variables
barriers
signals

main types of IPC

communication between processes
- transfer of data
  - once the data is transferred, the data is no longer available
  - byte streams
    - undelimited
    - no boundaries
  - messages
    - messages are packets of data
    - cant read a partial message
    - cant read more than one message at a time
  - pseudo files
    - files that are not actually files
    - can be read and written to
    - can be opened and closed
- shared memory
  - not actuall transfer of data but rather access to the same memory
  - super fast but can be dangerous
synchronization between processes
- semaphores
  - a counter that can be incremented and decremented
  - may never be less than 0
  - used to control access to a shared resource
  - counts like how many slots are available
- file locks
  - locks a file so that only one process can access it at a time
  - can be used to synchronize access to a file
  - can target a specific region of a file
- Mutexes and conditions
  - utilized by threads
  - prevents unsafe access to shared data
  - the difference between a mutex and the condition is that the condition is used to wait for a condition to be true so it is a blocking call
signalling between processes (kinda does both)