InterProcess Communication

Signal

• There can be hardware interrupts, but software interrupts as well
• GNU signal can be a great reference.
  • Linux relies on GNU
• Signal API → type of interrupt, handler
• Signal1.c
  • function pointer → address of the program
  • handler has no return but one input value; signal input is given
  • Check signal is whether Sigint
  • ctrl + c → now task to the program from the outside
  • It changes the control flow of the operation
• Signal2.c
  • Alarm signal
  • need to handle regular alarm
  • Timer interrupt occurs by a sec
  • by signaling, preemption happens and context switch as well
• Pipe1.c
  • Nonzero value → error
  • pipe is a kind of file
    • File is anything that can have stream of information
  • Parent and child has same file description information
  • Pipe works for reading and writing
  • If the value is broken, make to write remaining data (buffer)
  • Writing behavior depends on OS/ return sent value, it is because it has limited space of buffer
  • No more data comes to the pipe
  • 3 is reading pipe, 4 is writing pipe
  • reading happens up to 31 characters
  • Child and parent process
  • Through using file, parent and child process exchange their data
  • It is something shared exclusively
    • Doesn’t have global name to be not interrupted by other processes.
    • For one to one communication
  • Unnamed pipe → use to make communicate
  • multiple process invoked at same time, it is to difficult to clarify sender and messages
    • Synchronization
• Pipe2.c
  • duplicate operation
  • hello program is loaded
  • standard ouput goes to the pipe
  • Hello is executed, sent to the pipe and show up at the display
  • invoke the program at the middle of the program
  • Library → popen (read how to utilizte the API)
    • File is pipe
    • execution results is given to file actually