Ending tail -f started in a shell script

Question

I have the following.

1. A Java process writing logs to the stdout
2. A shell script starting the Java process
3. Another shell script which executes the previous one and redirects the log
4. I check the log file with the tail -f command for the success message.

Even if I have exit 0 in the code I cannot end the tail -f process.

Which doesn't let my script to finish. Is there any other way of doing this in Bash?

The code looks like the following.

function startServer() {   touch logfile   startJavaprocess > logfile &    tail -f logfile | while read line    do     if echo $line | grep -q 'Started'; then       echo 'Server Started'       exit 0     fi   done } 

Answer 1

The best answer I can come up with is this

1. Put a timeout on the read, tail -f logfile | read -t 30 line
2. Start tail with --pid=$$, that way it'll exit when the bash-process has finished.

It'll cover all cases I can think of (server hangs with no output, server exits, server starts correctly).

Dont forget to start your tail before the server.

tail -n0 -F logfile 2>/dev/null | while read -t 30 line 

the -F will 'read' the file even if it doesn't exist (start reading it when it appears). The -n0 won't read anything already in the file, so you can keep appending to the logfile instead of overwriting it each time, and to standard log rotation on it.

EDIT:
Ok, so a rather crude 'solution', if you're using tail. There are probably better solutions using something else but tail, but I got to give it to you, tail gets you out of the broken-pipe quite nicely. A 'tee' which is able to handle SIGPIPE would probably work better. The java process actively doing a file system drop with an 'im alive' message of some sort is probably even easier to wait for.

function startServer() {   touch logfile    # 30 second timeout.   sleep 30 &   timerPid=$!    tail -n0 -F --pid=$timerPid logfile | while read line    do     if echo $line | grep -q 'Started'; then       echo 'Server Started'       # stop the timer..       kill $timerPid     fi   done &    startJavaprocess > logfile &    # wait for the timer to expire (or be killed)   wait %sleep } 

Answer 2

Based on the answers I found here, this is what I've come up with.

It directly deals with tail and kills it once we've seen the needed log output. Using 'pkill -P $$ tail' should ensure that the right process is killed.

wait_until_started() {     echo Waiting until server is started     regex='Started'     tail logfile -n0 -F | while read line; do             if [[ $line =~ $regex ]]; then                     pkill -9 -P $$ tail             fi     done     echo Server is started }