Question

The title might be vague, but I have a good example:

echo "Test message:\nThis is a line.\nAnd this is another." | nail -s "`tail -1`" joe@localhost

The objective here is to send the content of the echo as the message body and using the last line as the subject. However, when I do this, I lose the body.

echo "Test message:\nThis is a line.\nAnd this is another." | nail joe@localhost

Works fine, but there is no subject.

Answer 1

You could do it with a named pipe, this works here:

mkfifo subj.fifo

echo "Test message:\nThis is a line.\nAnd this is another." |
  tee >(tail -n1 > subj.fifo) | mail -s "$(< subj.fifo)" joe@localhost

rm subj.fifo

Note if you use head instead of tail, you need to make tee ignore SIGPIPE signals, e.g. trap '' PIPE.