Need help with script

s_linux · 06-16-2010, 03:48 PM

Hi All,

I have a command which is application related and I get a output some thing like this when I execute the command...

Quote:

application running

So I need to write script to see if application is running, if application state running run some command else run echo command to state application is not running.

So I need to run the first command, then based on output (Application status), run the second command else echo command.
Help will be appreciated.

Thanks.

AlucardZero · 06-16-2010, 03:54 PM

http://www.freeos.com/guides/lsst/ch03sec03.html
http://www.freeos.com/guides/lsst/

MensaWater · 06-16-2010, 03:57 PM

if [[ $(command) = "application running" ]]
then this
else that
fi

Where:
command = the name of the command you're running.
this = the command(s) you want to run if it IS running.
else = the command(s) you want to run if it is NOT running.

s_linux · 06-17-2010, 10:23 AM

Thanks for your reply...
I have an other question with if command...

if i have a command something like this...

Quote:

if [[ $(tail -1 /var/opt/tmp/application.log) = "Application - error" ]; then
echo "Application is not running"
else
echo "some command"

that works great if tail command exactly the same as "Application - error" and if it is not the same, let's say some thing like "Application - error errorcode" how can we define that. Error code wont be the same all the time.

Thanks once again.

MensaWater · 06-17-2010, 12:28 PM

Code:

if tail -1 /var/opt/tmp/application.log | grep "Application - error"
then
echo "Application is not running"
else
echo "some command"

The return code of the grep command will be non-zero (false) if the text you're looking for isn't found. You can see that by typing the first line (without the if) at command line and hitting return then typing "echo $?". If it finds it the $? will be 0 - if not it will be non-zero (typically 1 unless some other error occurs).

Note that "-" is used for signifying flags so you might have to escape it so grep knows you're looking for literal "-" by prepending it with a "\".

Also it seems you need negation here - put a "!" after the if to negate what follows it.

s_linux · 06-18-2010, 08:52 AM

Thanks for your help, that is really works...

But I'm confused with this

Quote:

Also it seems you need negation here - put a "!" after the if to negate what follows it.

I don't really understand. if Could you please give me little more info on it that would appreciated.

Thanks again.

MensaWater · 06-18-2010, 09:37 AM

Disregard it - I misread what you were attempting to do.

You're saying if you see "error" it means the application isn't running. I was thinking you wouldn't see anything if the application isn't running so would need to negate it but that isn't the case.

Negation is sometimes needed if you're only doing an "if" and "then" but not an "else".

For example if you ran:

Code:

ps -ef |grep -v grep |grep java

It returns a zero exit status if it is running and a non-zero exit status if it isn't.

If you wanted to only do something if it was NOT running then you'd do:

Code:

if ! ps -ef |grep -v grep |grep java
then java -xm (etc...)
fi

That would tell it to start the java process you're interested in ONLY if it is not running.