These examples illustrate how to use the standard Unix library functions, for making system calls, and interacting with the operating system.

speak.c should be compiled and executed at the same time as tick.c. These deal with FIFO writing, and reading, respectively. Much like the networking examples, which read from and write to sockets, speak.c and tick.c must both be running at the same time. One program will read a string from the user, and the other will print the received string to demonstrate the connectivity.

daemon.c and fork.c deal with the fork() function and child processes. pipe.c creates a pipe, forks itself, and communicates with its child process through the pipe.

ls.c is a simple directory listing. It accepts a directory as an optional argument, for example ”$ ./ls ~/Documents”.

shell.c is a very simple shell that sends lines from stdin to system(), or /bin/sh. It has only two built-in commands, “cd” and “exit”.