How Linux Works

Here Documents

Sometimes you want to print a large section of text or feed a lot of text to another command. Rather than using several echo commands, you can employ the shell's here document feature.

The following is a script that shows how here documents work:

#!/bin/sh
DATE='date'
cat <<EOF
Date: $DATE

The output above is from Unix date command.
It's not a very interesting command.
EOF

The items in bold control the here document. <<EOF tells the shell to redirect all lines that follow to the standard input of the command that precedes <<EOF, which in this case is cat. The redirection stops as soon as the EOF marker occurs on a line by itself. The marker that you use doesn't have to be EOF — use any string that you like, but remember that you ...