Start a command, count lines of output after 10 seconds, then either restart it or let it run

Question

I have an interesting situation I am trying to script. I have a program that outputs 26,000 lines after 10 seconds when it starts successfully. Otherwise I have to kill it and start it again. I tried doing something like this:

test $(./long_program | wc -l) -eq 26000 && echo "Started successfully"

but that only works if the program finishes running. Is there a clever way to watch the output stream of a command and make decisions accordingly? I'm at a loss, not quite sure even how to start searching for this. Thanks!

score 4 · Accepted Answer · answered Aug 18 '12 at 08:18

4

What about

./long_program > mylogfile &
pid=$!
sleep 10

# then test on mylogfile length and kill $pid if needed

answered Aug 18 '12 at 08:18

Stephane Rouberol

4,286
19
18

That's actually really simple and straight forward. – nathancahill Aug 18 '12 at 08:45

Ted Shaw · Answer 2 · 2012-08-18T10:52:58.600

0

count=0
until [ $count -eq 26000 ]; do
    killall ./longrun
    #start in background
    ./longrun >output.$$ &
    sleep 10
    count=$(wc -l output.$$ |awk '{print $1}')   
done
echo "done"
#disown so it continues after current login quits
disown -h

edited Aug 18 '12 at 10:52

answered Aug 18 '12 at 08:26

Ted Shaw

2,298
14
8

Wow never knew about disown. I will be using that for sure. – nathancahill Aug 18 '12 at 08:45
1

[Don't use kill -9](http://stackoverflow.com/a/690631/347411), also kill does not read stdin, so that pipline won't work. See http://mywiki.wooledge.org/ProcessManagement – geirha Aug 18 '12 at 10:21
i replaced it with killall to keep it simple – Ted Shaw Aug 18 '12 at 10:55
1

Still better to kill by pid, if you would ever want to run multiple instances. – tripleee Aug 18 '12 at 14:32

Start a command, count lines of output after 10 seconds, then either restart it or let it run

2 Answers2