Pass content of file in variable into bash script - without writing the file down

Question

I have a bash script like

./script -a filename

And I have the content of a file in a variable $CONTENT

How can I pass the variable into the command. I mean I could write the content of the variable down to disk first, but that seems to be too much overhead.

Is there a better solution?

Something like

./scrip -a << $CONTENT

Answer 1

You need one more < :

./script -a <<<"$CONTENT"

<<< is called a herestring, and takes the following string and passes it as the standard input.

Answer 2

Kevin's suggestion to use a here string will work, as long as you quote the variable as suggested in the comments to that answer. A more portable solution is to use a here doc:

./script -a << EOF
$CONTENT
EOF

In this case, quotes are not necessary and indeed undesirable.