11.9 Here Documents
Say 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 use the shell’s here document feature, as shown in the following script:
#!/bin/sh
DATE=$(date)
cat <<EOF
Date: $DATE
The output above is from the 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 subsequent lines 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 can actually be any string, but remember to use the same marker at the beginning and end of the here document. Also, convention dictates that the marker be in all uppercase letters.
Notice the shell variable $DATE in the here document. The shell expands shell variables inside here documents, which is especially useful when you’re printing out reports that contain many variables.