Working with cat EOF in bash
This post has been fully copied from the stackoverflow page https://stackoverflow.com/questions/2500436/how-does-cat-eof-work-in-bash
The cat <<EOF syntax is very useful when working with multi-line text in Bash, eg. when assigning multi-line string to a shell variable, file or a pipe.
Examples of “cat «EOF syntax usage in Bash”:
Assign multi-line string to a shell variable
$ sql=$(cat <<EOF
SELECT foo, bar FROM db
WHERE foo='baz'
EOF
)
The $sql variable now holds the new-line characters too. You can verify with echo -e "$sql".
Pass multi-line string to a file in Bash
$ cat <<EOF > print.sh
#!/bin/bash
echo \$PWD
echo $PWD
EOF
The print.sh file now contains:
#!/bin/bash
echo $PWD
echo /home/user
Pass multi-line string to a pipe in Bash
$ cat <<EOF | grep 'b' | tee b.txt
foo
bar
baz
EOF
The b.txt file contains bar and baz lines. The same output is printed to stdout.