BASH- Hold script until all contents of a file is written

Shell Programming and Scripting
1

I have to hit a very large database to pull fields of information.

I have a script that runs multiple instance of the same query against the data base and writes contents to a file.

The script terminates before the file is completely written to confirmed by

ps -ef | grep <script name>

The code below will hold the script until the file is created.
But I also want to know when writting has completed.

I guess my question is how do I look for EOF ?

while true 
do 
 [ -f resultfile ] && break
 sleep 2 
done

Thanks alot in advance !

2

Perhaps you could try using either lsof or fuser to see when whatever process is writing to the file has ceased.

3

It is the application's job to tell you when it is done. It's very difficult and unreliable to try and detect the other way.

4

If you can't get the first applicaiton to manipulate a lockfile or otherwise signal your script, you can use incron (a cron like utility for file system events) to signal your second script that it is safe to read.

I use incron to detect the close file event for any file in my public ftp submission directory and as soon as it is done being uploaded, incron launches a script that yanks it away to a non-public directory so that every individual's uploads are private to other users whithout giving everyone a different area.

I also have a web interface to reboot my server, turn on and off anonymous FTP, share or not share my media directories (on/off or for a timeout period), etc. I know very little CGI, so instead of handling it in CGI, I save the state of the user radio button clicks and password hash to a text file and use Incron to detect a change and launch a shell script which parses and interperates it. I did it out of ignorance of CGI but I believe it is very secure.

Mike

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