Pipes

1
Pipes

• One-way channel joining two processes
• Read/write sends data through pipe
• Function pipe( ) establishes pipe
• int pipe (int filedes )
• filedes int2 file descriptors identifies pipe.
  
• If pipe call successful
• filedes0 opened for reading from the pipe, and
• filedes1 opened to write to the pipe.

2
Connecting Processes

• Create the pipe
• Fork to create the reading child
• In child, close the writing end of the pipe, and
  do any other required preparations
• In child, execute the child program
• In parent, close the reading end of the pipe
• If a second child is to write to the pipe, create
  that child, make appropriate preparations, and
  execute its program. If the parent is to write,
  do so at this time

3
Advanced Techniques

• Record Locking - process temporarily reserves
  part of a file for its own exclusive use.
• Message Passing - allows process to send and
  receive messages (bytes or characters).
• Semaphores - provides means for process
  synchronization
• Shared Memory - permits two or more processes to
  share data contained in specific memory segments.