How to ask bash to wait for a result and send a SIGKILL when it get it ?

Question

I want to use zbarcam but after reading a barcode, it doesn't stop.

$ zbarcam | xvkbd -file - -window emacs
EAN-13:6941428130969
CODE-128:3096140900557

Do you know how I can tell bash to kill zbarcam after printing on the stdout the first \n ?

Answer 1

Try

tmp=/tmp/barcode.$$ # Note: security risk
zbarcam > $tmp &
pid=$!
# Sleep until file has content
while [[ ! -s $tmp ]] ; do
    sleep 1
done
kill $pid
cat $tmp

Note that it might not work if zbarcam doesn't flush its output.

Answer 2

Have you tried this?

zbarcam | head -1 | xvkbd -file - -window emacs

Answer 3

tmp=/tmp/barcode.$$ # Note: security risk zbarcam > $tmp & pid=$!

Sleep until file has content

while [[ ! -s $tmp ]] ; do sleep 1 done kill $pid cat $tmp

Very Good :D