Slide 2.11: Advanced Unix shell commands

Slide 2.10: Built-in Unix shell commands
Slide 3.1: Programming Exercise I: an on-line music store using files
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Advanced Unix Shell Commands

Redirection
It is to send the input or output of a process to a location other than the standard one.

The symbol ‘>’ is used to redirect the standard output of a process. By placing ‘>’ after a command and following this with the name of a file, the output of the command will go to the specified file instead of the screen. If you would like the output of a program to be appended to a file, as opposed to overwriting it as discussed above, you can use “>>” to redirect the output to a file.

The symbol ‘<’ is used to redirect the standard input of a process. By placing ‘<’ after a command and following this with the name of a file, the input for the command will be taken from the specified file instead of the keyboard.

Pipe
A pipe is a method of inter-process communication (IPC) which allows a one-way flow of information between two processes on the same machine. The character ‘|’ is used to create a pipe between two processes.

/bin/sort
It is a shell command that sorts lines of text files. The command “cat unix.pl | sort” is the same as the command “sort unix.pl” .