How do you type a tab in a bash here-document?

Question

The definition of a here-document is here: http://en.wikipedia.org/wiki/Here_document

How can you type a tab in a here-document? Such as this:

cat > prices.txt << EOF
coffee\t$1.50
tea\t$1.50
burger\t$5.00
EOF

UPDATE:

Issues dealt with in this question:

1. Expanding the tab character
2. While not expanding the dollar sign
3. Embedding a here-doc in a file such as a script

Answer 1

For me, I type ctrl-V followed by ctrl-I to insert a tab in the bash shell. This gets around the shell intercepting the tab, which otherwise has a 'special' meaning. Ctrl-V followed by a tab should work too.

When embedding dollar signs in a here document you need to disable interpolation of shell variables, or else prefix each one with a backslash to escape (i.e. \$).

Using your example text I ended up with this content in prices.txt:

coffee\t.50
tea\t.50
burger\t.00

because $1 and $5 are not set. Interpolation can be switched off by quoting the terminator, for example:

cat > prices.txt <<"EOF"

Answer 2

You can embed your here doc in your script and assign it to a variable without using a separate file at all:

#!/bin/bash
read -r -d '' var<<"EOF"
coffee\t$1.50
tea\t$1.50
burger\t$5.00
EOF

Then printf or echo -e will expand the \t characters into tabs. You can output it to a file:

printf "%s\n" "$var" > prices.txt

Or assign the variable's value to itself using printf -v:

printf -v var "%s\n" "$var"

Now var or the file prices.txt contains actual tabs instead of \t.

You could process your here doc as it's read instead of storing it in a variable or writing it to a file:

while read -r item price
do
    printf "The price of %s is %s.\n" $item $price    # as a sentence
    printf "%s\t%s\n" $item $price                  # as a tab-delimited line
done <<- "EOF"
    coffee $1.50    # I'm using spaces between fields in this case
    tea $1.50
    burger $5.00
    EOF

Note that I used <<- for the here doc operator in this case. This allows me to indent the lines of the here doc for readability. The indentation must consist of tabs only (no spaces).

Answer 3

TAB="$(printf '\t')"

cat > prices.txt << EOF
coffee${TAB}\$1.50
tea${TAB}\$1.50
burger${TAB}\$5.00
EOF