Lab 1 Overview

Mimic the pipe operator in the shell:

ls | cat

./pipe ls cat

Two main pieces

1. Spawning a process
2. Piping a process (using file descriptors)

Spawning a new process

• fork splits the current process
• wait waits for the other fork
• exec executes another process

fork

• On fork() will create another process—exact same copy including the execution state
• Can distinguish based on the return from fork()
  • If the return value is 0, we’re in the child process
  • Greater than 0, in the parent process
  • Less than 0, error

exec

• Will completely replace itself with another program
• Code and address space of original completely lost
• Any code after child process won’t run
• execve(pathname, argv, environmentvars)