Shell Programming and Scripting

I would like to write a program that run every second.

In this program, I would retrieve data from a SQL db
and redirect the firefox to the appropriate place if the checking of SQL is success

As I really consider the performance and complexity of coding, is shell script a good choice? or other programming like Java would be better?

Thanks for any suggestions or comment.

then you better cron that job

try sleep command to sleep for a particular amount of time and then start again or schedule the script in cron tab to run as you want it.

Thank you for both replies

1. cron job cannot be executed in seconds, minimum is 1 minute

2. I tried to use sleep command, but I have a question

while [condition]
<<my command>>
sleep 1
do

1) if the command executes in 0.5s the total time for one process would be 1.5s?
2) And the execute time should be undetermined, the total time of each execute may be 1.5s, 1.8s, etc...?

True with regards to what you said about cron. To work around that you can setup a cron to execute that script every minute. Within the script you might have something like:

command
sleep 10
command
sleep 10

^^etc. etc. You can change the frequency of course but something like that should work. Java would be less resource intensive for the server since it's client based. I'm not a big fan of java but I would try both on a test box or whatever then make my determination from there.

-- edited

oops...
missed the part about the frequency you posted and can now see why you asked about java. But going back to what you were asking:

Keep in mind that it's not one process but two seperate processes. One for the command while another for sleep. So in theory, (better to let one of the vets here confirm), you might see two or three executing at the same time during top. If you're on shared then you may want to go with java to keep your host from nagging you about using up all of the servers resources. Lastly, if you're sql server is on another host, take into consideration what might happen if that server starts to lag drastically. You will need to keep tabs on the execution times from within the sql logs.

Thank you for your reply
I will test the result of sleep command

building on the first example to run a script every minute, something like this maybe?

Code:

while 1;
do
    first=`date +%s`
    exec_script &
    while 1;
        do second=`date +%s`
            result=`expr $second - $first`
            if `expr $result > 1` 
                 break;
        done;
done;

I'm not sure about the syntax though