[SOLVED] How can I stop a function called in a script?

rylphs · 09-30-2010, 06:25 AM

Hello,

I made the following script:

Code:

#!/bin/bash

logErrors(){exec 2>/tmp/errorlogfifo
while true
do
cat /tmp/errorlogfifo |echo $(date "+[%Y-%m-%d %H:%m:%S]") Error: >/var/log/error.log
done}

logErrors
ls inexistentFile
exit 0

If I execute the script I see the formated error message in /var/log/error.log, as to be expected. After the script execution, I hoped "logErrors" was not executing anymore, but when, in another terminal, I call "echo something > /tmp/errorlogfifo", I still see the formated error message "something" in "/var/log/error.log". How can I finalize "logErrors" before the script ends? Or, maybe someone knows a better way to format and log the erros in a script.

I forgot to say that the file "/tmp/errorlogfifo" is a named pipe created by the command "mkfifo /tmp/errorlogfifo".

Sorry for my bad English.
Thanks.

grail · 09-30-2010, 06:50 AM

Well the way I understand it, you need to save your fd to another and then call it back later.

Code:

exec 3>&2 2>/tmp/errorlogfifo

<do your stuff>

exec 2>&3 3>&-

rylphs · 09-30-2010, 07:23 AM

Quote:

Originally Posted by grail

Well the way I understand it, you need to save your fd to another and then call it back later.

Code:

exec 3>&2 2>/tmp/errorlogfifo

<do your stuff>

exec 2>&3 3>&-

Sorry if I was not clear enough, but what I want, is to catch all the errors in the script, format them and send to a log file. To do that, I redirected the stderr to a namedpipe and I used a function that is allways reading (in a infinite loop) the content of that pipe, formatting and sending it to a log file. But the problem is that the function still running after the script ends. Even If i close the shell that executed the script, the function keeps running.

I am already doing what you suggested inside the "logErros" function (without recovering the default state of the descriptor).

Thank you for you suggestion.

grail · 09-30-2010, 07:34 AM

hmmm ... so if it an infinite loop, how is the script stopping?

doublejoon · 09-30-2010, 07:54 AM

Could you add at end of your function?

Code:

echo && > /tmp/logerrors.pid
kill $(cat /tmp/logerrors.pid)

rylphs · 09-30-2010, 08:29 AM

Quote:

Originally Posted by grail

hmmm ... so if it an infinite loop, how is the script stopping?

I really sorry because I missed something. I was calling the function with the "&" symbol. I had changed my script to test, and I forgot to undo the change. So, the correct script is:

Code:

#!/bin/bash

logErrors(){

    exec 2>/tmp/errorlogfifo

    while true

    do

        cat /tmp/errorlogfifo |echo $(date "+[%Y-%m-%d %H:%m:%S]") Error: >/var/log/error.log

    done

}

logErrors& #I missed the "&" I added.
ls inexistentFile
exit 0

It seems that in a call of a function in background, kernel keeps a process, with the same name of the script, running the function in memory. Am I correct?

I noticed I don't need the while loop. If I just have the "cat" call everything works fine.

I have another doubt, Is there some way to discover the ID of the function I called in background. I tried the $PPID variable, but the $PPID of the script is different from the PID of the process kept running.

Thank you and sorry for the trouble.

rylphs · 09-30-2010, 08:32 AM

Quote:

Originally Posted by doublejoon

Could you add at end of your function?

Code:

echo && > /tmp/logerrors.pid
kill $(cat /tmp/logerrors.pid)

Sorry, but what exactly these call do?

grail · 09-30-2010, 09:54 AM

So a little searching and playing I found this:

Code:

MYPID=$(jobs -p)

Now you should be able to kill it in the appropriate place before exiting your script.

rylphs · 09-30-2010, 10:52 AM

Quote:

Originally Posted by grail

So a little searching and playing I found this:

Code:

MYPID=$(jobs -p)

Now you should be able to kill it in the appropriate place before exiting your script.

I've found another solution:

Code:

#!/bin/bash

logErrors(){
    scriptPid=$$
    while ps -p $scriptPid
    do
        cat /tmp/errorlogfifo |echo $(date "+[%Y-%m-%d %H:%m:%S]") Error: >/var/log/error.log
    done&
}

logErrors
ls inexistentFile
exit 0

Instead of have to kill the process, the function runs only while the script is running.

I still am having some problems, but it's another problem. I'll mark this thread as solved. Thank you everybody for the help.