[SOLVED] BASH: if statement (check if process exists and then...)

cober · 09-12-2011, 02:48 AM

Hey all,

I have a little problem with my script, so I'm asking you to help me.

First of all, I want to pack all files (*/*) in RAR and since RAR isn't supporting multithreading in *NIX I wrote this script.

rar:

Code:

for FILENAME in */*

        do
        cd ${FILENAME%/*}
        RARNAME=`dd if=/dev/urandom count=128 bs=1 2>&1 | md5sum | cut -b-16`; screen -d -m rar a -hppassword -m0 -v2147483648b $RARNAME.rar "$1";

   done

exit 0

Ok, this one is going to run in background using screen so I'll be able to use more than 1 CPU for adding files to rar.

Now, where's my problem (and my lack of knowledge) appears..

I also made a script which checks if screen process is running

Code:

if [ "$(pidof SCREEN)" ]
then
echo was found.
else
echo not found.
fi

Now please help

My idea:

Code:

if [ "$(pidof SCREEN)" ]
then
echo was found.
sleep 20
i want to check it again in 20sec and if there is no more screen process to proceed, otherwise to check again in 20sec and on and on..
else
echo not found.
fi

Don't even know how is this called.. any help really appreciated!

corp769 · 09-12-2011, 03:04 AM

Hello,

Looks like you are looking for a while loop? Something like the following pseudo-code:

Code:

while pidof screen is true
  do this
  sleep 20

Note that I am not on linux right now, so I can't really code this up and test it for you. Hope this helps!

Cheers,

Josh

cober · 09-12-2011, 03:20 AM

corp769, thanks for this tip.

I want to know how to do it repeatedly, like to check in my example 20sec interval, and to proceed if there's no screen process running, otherwise to just check every 20sec for a screen process.

corp769 · 09-12-2011, 03:30 AM

Maybe what you could do is create an absolute true while loop, and have the if statement within it. From there, it will keep looping regardless because you are telling it to loop infinitely. Then within the while loop, have your for and sleep statements, and you should be set. Of course you would want to set it up where depending on whatever variable or what not, you will want to break out of the while statement.

cober · 09-12-2011, 03:44 AM

Uh, this is far more complicated than I just thought at first. Nevermind, I will check for these processes manually. Thanks!

grail · 09-12-2011, 04:17 AM

I am not sure I understand what is so complicated? Did you not understand the while loop?

cober · 09-12-2011, 04:22 AM

grail: I'm not really into bash scripting, so it's not that easy for me. I thought there's just a simple way to make this work but since I lack some bash knowledge I'll just check manually 'ps -aux' and then run other script.

cober · 09-12-2011, 04:26 AM

Full script is:

Code:

sab restart
antidelete
# Naredi screenshote brez da zajame rar fajle
find /home/cober/downloads/*/* -not -name "*.rar" | while read file; do
  mtn -f /usr/local/tahomabd.ttf -r 3 -w 900 "$file"
done
if [ "$(pidof SCREEN)" ]
then
echo was found.
sleep 20
==> my issue <== (if proc exists, check once more, if exists, once more etc., otherwise proceed.)
else
find /home/cober/downloads/*/* -maxdepth 1 -not -size +2G -not -name "*.jpg" | while read file; do
  ncftpput -b -u username -p pass ftp.domain.com . "$file"
fi
done
echo "Slike....:"
getm
du -h *

antidelete:

Code:

for FILENAME in /home/cober/downloads/*/*

        do
        cd ${FILENAME%/*}
        RARNAME=`dd if=/dev/urandom count=128 bs=1 2>&1 | md5sum | cut -b-16`; screen -d -m -S 1 rar a -hppassword -m0 -v2147483648b $RARNAME.rar "$1";

   done

exit 0

grail · 09-12-2011, 05:49 AM

So if I understand correctly you wish to have the if be continuous until SCREEN does not exist ... yes?

In that case employ the loop that was suggested in place of the if and remove the else:

Code:

while pidof SCREEN; do sleep 20; done

find /home/cober/downloads/*/* -maxdepth 1 -not -size +2G -not -name "*.jpg" | while read file; do
  ncftpput -b -u username -p pass ftp.domain.com . "$file"; done

This will loop and pause for 20 seconds each time before checking again to see if SCREEN is running.

Reuti · 09-12-2011, 06:42 AM

Going back to the beginning: why do you use screen for the processes, instead of running it in the background by appending an & at the end of the command? Then you can list the running instances with jobs and wait for the completion by a wait command in shell script.