Input and Output Redirection

The operating system allows you to manipulate the input and output (I/O) of data to and from your system by using specific I/O commands and symbols. You can control input by specifying the location from which to gather data. For example, you can specify to read input while data is entered on the keyboard (standard input) or to read input from a file. You can control output by specifying where to display or store data. You can specify to write output data to the screen (standard output) or to write it to a file.

The operating system, because it is multitasking, is designed to handle processes in combination with each other. This chapter discusses the advantages of redirecting input and output and of tying processes together.

This chapter discusses the following:

• Standard Input, Standard Output, and Standard Error
• Redirecting Standard Output
• Redirecting Output to a File
• Redirecting Output and Appending to a File
• Creating a Text File with Redirection from the Keyboard
• Concatenating Text Files
• Redirecting Standard Input
• Discarding Output with the /dev/null File
• Redirecting Standard Error and Other Output
• Using Inline Input (Here) Documents
• Using Pipes and Filters
• Displaying Program Output and Copying to a File (tee command)
• Clearing Your Screen (clear Command)
• Sending a Message to Standard Output (echo Command)
• Appending a Single Line of Text to a File (echo Command)
• Copying Your Screen to a File (capture and script Commands)
• Displaying Text in Large Letters on Your Screen (banner Command)
• Command Summary for Input and Output Redirection