Redirection

Redirection characters change where a command gets information from or sends information to.

Redirecting Command Input and Output

Unless you specify otherwise, Windows NT receives input from your keyboard and sends output to your screen. Sometimes it is useful to redirect the input or output to a file or a printer. For example, you might want to redirect a directory listing from the screen to a file.

To redirect the input or output of a command, you use one of the following redirection characters:

The greater-than sign (>) sends the output of a command to a file or a device, such as a printer.

The less-than sign (<) takes the input needed for a command from a file rather than from the keyboard.

The double greater-than sign (>>) adds output from a command to the end of a file without deleting the information already in the file.

Redirecting the Output of a Command

Almost all commands send output to your screen. Even commands that send output to a drive or printer also display messages and prompts on your screen.

To redirect the output from the screen to a file or printer, use the greater-than sign (>). You can use the greater-than sign with most Windows NT commands. For example, in the following command, the directory listing produced by the dir command is redirected to the DIRLIST.TXT file:

dir > dirlist.txt

If the DIRLIST.TXT file doesn't exist, Windows NT creates it. If DIRLIST.TXT exists, Windows NT replaces the information in the file with the output from the dir command.

To add the output from a command to the end of a file without losing any of the information already in the file, use a double greater-than sign (>>). For example, in the following command, the directory listing produced by the dir command is appended to the DIRLIST.TXT file:

dir >> dirlist.txt

Note

Some command output, such as error messages, may not be redirected when using the greater-than sign (>).

Redirecting the Input to a Command

Just as you can send the output of a command to a file or printer rather than to your screen, you can take the input for a command from a file rather than from the keyboard. To take input from a file, use the less-than sign (<). For example, the following command takes the input for the sort command from the LIST.TXT file:

sort < list.txt

Windows NT alphabetizes the lines of the LIST.TXT file and displays the result on your screen.