starting and killing evince process in a loop

Question

I have certain PDF files. I want to inspect each of them for 20 seconds. The way I was trying to do that is like following: for file in *.pdf; do echo $file; evince $file; sleep 20s; killall evince; done . It displays the first file, but does not kill it after 20s. What is going wrong here?

Answer 1

Note that you don't have to kill all: you can kill the specific instance:

for file in *.pdf; do
    echo "$file"
    evince "$file" &
    sleep 20s
    kill $!           
done

$! is the pid of the most recently backgrounded process. (http://www.gnu.org/software/bash/manual/bashref.html#Special-Parameters)

Answer 2

I think you just forgot to run evince in background:

for file in *.pdf; do echo $file; evince $file &; sleep 20s; killall evince; done

Notice the & after the evince command.