Shell Programming and Scripting

I have 2 servers syncing some directories with an rsync script. They are in different countries. The rsync script is executed on Server#1. I am using 'fswatch' to execute the script automatically, when the directory is modified.

Here is where I am looking for help:

After 'fswatch' see's a directory change, it triggers my rsync script on Server#1. I need the rsync script to look at the Server#2 and check a file which contains the string "open" or "closed". If it says "closed", I want the rsync to script to execute. If it says "open", I don't want the rsync script to execute, but rather wait x seconds and check the file again (the file will eventually change to "closed", allowing the script to run).

Any insight on structuring this is greatly appreciated, I haven't figured out how to setup the loop of 'check file/don't execute/wait/check again' logic.

---------- Post updated at 08:06 PM ---------- Previous update was at 06:44 PM ----------

I think I found the logic. Can somebody tell me how to get this to time out after say 100 tries?

Code:

STATUSFILE=/Users/patrick/Desktop/temp/remoteserverstatus
until grep -q closed "$STATUSFILE"; do
echo ‘waiting for sever to finish’; sleep 3
done
echo ‘running script’

You didn't say what shell or operating system you're using. With any shell that accepts POSIX standard shell syntax, you could try the following simple change to your script:

Code:

STATUSFILE=/Users/patrick/Desktop/temp/remoteserverstatus
n=0
until grep -q closed "$STATUSFILE"; do
        n=$((n + 1))
        if [ $n -ge 100 ]
        then    echo 'server unavailable'
                exit 1
        fi
        echo 'waiting for sever to finish'
        sleep 3
done
echo 'running script'

Note the changes to the quotes used on your echo commands in addition to the added code.

Wrap the until in a for loop 1 .. 100, and write sleep x after until done inside for loop
And if the status is closed, give a break to exit out of the for loop

I got the impression from reading your posting that the status file (the one containing "closed" or "open") was on the remote server. If so, then the "grep" command of a local file won't help.

If the status file IS local to the server running the script, then Don Cragun's script looks good. But for some reason I think you're trying to check a status file on the remote end before starting the "rsync" locally?

You are correct. The script initially checks the remote file and creates a local copy which is used for authorizing rsync in the until loop. I know, its an extra step I should probably optimize by looking straight at the server.

---------- Post updated at 12:34 AM ---------- Previous update was at 12:23 AM ----------

Don, I like this a lot. I'm going to deploy it on Monday in my test environment but based on the test I've done so far, this works great. Thanks!

BASH/MACOSX10.7

Unless there is something external to the script I gave you that updates /Users/patrick/Desktop/temp/remoteserverstatus when the remote server status changes, the script I gave you will never succeed if the remote server is busy when the loop starts.

Basically, these servers are both running this program. The folders that are being synced are AFP share points that are used by people to upload files over a network. The idea is each country has a local repository of data, for performance measures.

The program reaches out to the far server and grabs the status, and uses that for rsync authentication. This is just to prevent synonymous syncing, which is problematic when large files upload to afp. The server will start the rsync before the file is finished uploading to the AFP share point, causing this chain reaction of syncing partly uploaded files between both servers.

i REALLY wanted to simply have the rsync wait until any AFP upload is done, but fswatch triggers the rsync when a change is made to the folder, including the start of the upload. I didn't see a way to have the script identify if a file was still uploading (there is nothing unique about a file upload-in-progress to use as a conditional for the script?)

Code:

n=0
until
    ssh user@servaddress 'cat /Users/admin/localserv/localserverstatus' 1> $REMOTESTAT && grep -q Closed "$REMOTESTAT"; do
        n=$((n + 1))
        if [ $n -ge 1000 ]
        then    echo 'server unavailable'
        exit 1
        fi
    echo 'waiting for sever to finish'
done
echo 'Open' 1> $LOCALSTAT
rsync -rvza --delete-after --progress $LOCALFOLDER $REMOTEFOLDER
echo 'Closed' 1> $LOCALSTAT