Input and Output Redirection

In almost all command line environments, we have the concept of

  1. A standard input device, normally the keyboard (STDIN=0)

  2. A standard output device, normally the screen (STDOUT=1)

  3. A standard error device, also normally the screen (STDERR=2)

You may have seen these in the Linux shell, and we can also use them in Windows/DOS.

At the command prompt, try typing 

ls -l > rubbish.txt

and check what happened by typing ls. You should have a new file called rubbish.txt with whatever the output of the ls -l command was. You can check the contents with the command 

more rubbish.txt

and you should do this. We have redirected the output of a command to a file using the operator >. This operator will create or overwrite the file. If we use the >> operator, it will append to the file.

Now try the help command and look through the output. We need to become familiar with some of these commands, but we need to know how to identify all of them. Type 

help > MyHelpFile.txt

and check to see that you have created a text file with a full listing of commands.

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