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Turn null value into 0 with a Bash Script

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Top Forums Shell Programming and Scripting Turn null value into 0 with a Bash Script
# 1  
Old 06-12-2014
Turn null value into 0 with a Bash Script
Hi,

I'm trying to make a bash script that if a null value is returned then to output the value 0.

I would like a script to search the 'top' tree and return the CPU value of a process, however if the process is not running for it to return 0 or another identifier.
Code:
top -b -n1 | awk '/ PROCESS /{print $9}'

Any help appreciated.


Moderator's Comments:
Mod Comment Please use code tags for your code and data, thanks
Last edited by vbe; 06-12-2014 at 04:27 PM..
# 2  
Old 06-12-2014
Try this:

Code:
top -b -n1 | awk '/ PROCESS /{CPU+=$9} END { printf "%03.1f\n",CPU }'

# 3  
Old 06-12-2014
Perfect thank you.

I'm not sure how, but it worked.

Many thanks.
# 4  
Old 06-12-2014
I'll try and explain CPU+=$9 is equivalent to CPU=CPU+$9, so you can see we are adding up all the CPU for all lines that match your process.

END { printf "%03.1f\n", CPU } when the end of input is reached the total CPU is printed, the format of printf is a little tricky (man printf may be of help here).
In this case we are forcing 1 decimal place and require a leading zero if value is less than 1 (eg 0.5).
# 5  
Old 06-12-2014
Thanks for your explanation. That makes sense. I have not used printf before, seems like it come in handy.

Cheers, for all your help.
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