如何要求bash等待结果并在收到结果后发送SIGKILL？

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

你有尝试过吗？

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