[SOLVED] Search file and then add one to its total

orangepeel190 · 08-07-2016, 09:22 PM

Hi all,

I am trying to work thru a problem.

I have a file, that only contains a number (starting at 09). I am trying to run a script that reads that file and then adds 1 to it up to a certain value (42). Once that output in the file gets to 42, it resets to 9.

Code:

#!/bin/bash
##############################
Counter=/home/Counter
##############################

	if [ cat "$Counter" -eq 43 ] ; then
		echo " Resetting the Counter"
		9 > $Counter
	else
	$Counter="`cat $Counter`+1"
	fi
exit 0

I am hoping that the output to "Counter" will be a number that increases by 1 each time the script it run (once per week). Once the script gets to 43, it will reset the value in the "Counter" file to 9.

What am I missing? I hope I am getting close, but I am puzzled as to how to make this work

Any thoughts/comments/suggestions would be appreciated.

grail · 08-07-2016, 09:48 PM

First thing I would say is to be consistent with your information. Initially you have advised the value in the file will be '09', but when you reset the value it will be '9' ... why not '09'?

As for your current code, you have a few issues:

1. It is recommended in bash to use [[]] over [] (see here for more details)

2. cat "$Counter" - This will output data to the screen and is not for being tested. You would need to use process substitution and prefer $() over `` (see here for more details)

3. 9 is not a command and hence cannot be redirected anywhere. Think of what command you would use to show a 9 on screen

4. $ is not used on the left of the equals sign in general. If it were, you would be saying the following:

Code:

/home/Counter="..."

5. "`cat $Counter`+1" :- see previous information on using $() instead, but this is still wrong as it will return a string as follows (assuming '09' is in file)

Code:

Counter="09 + 1"
echo $Counter
09 + 1

As you can see the above is not the desired output or affect

6. Further to the above, you need to look up the use of either the 'let' command or (()), I prefer the latter as easy to spot in code and a little clearer

Let us know how you get on

orangepeel190 · 08-07-2016, 10:03 PM

Thanks for your reply.

Yes, I did mean just 9

Thank you for your guidance. I have the script up and running now.

Appreciate your help!

grail · 08-07-2016, 10:53 PM

Don't forget to show the working script so others may learn from your experience