pbsnodes and bash string matching

I have a string of the form: "8, 14-24, 30-45, 9", which is a substring of the output of pbsnodes. This shows the cores in use on a given node, where 14-24 is a range of cores in use.

I'd like to know the total number of cores in use from this string, i.e. 1 + (24 - 14 + 1) + (45 - 30 + 1 )+ 1 in this example, using a bash script.

Any suggestions or help is much appreciated.

Michael

Solution

You could use pure bash techniques to achieve this. By reading the string to array and doing the arithmetic operator using the $((..)) operator. You can run these commands directly on the command-line,

IFS=", " read -ra numArray <<<"8, 14-24, 30-45, 9"

unset count
for word in "${numArray[@]}"; do
   (( ${#word} == 1 )) && ((++count)) || count=$(( count +  ${word#*-} - ${word%-*} + 1  ))
done

printf "%s\n" "$count"

The idea is

The read with -a splits the string on the de-limiter set by IFS and reads it into the array numArray
A loop on each of the elements, for each element, if the element is just single character, just increment total count by 1
For numeric ranges, do manipulation as e.g. for number a-b use parameter expansion syntax ${word#*-} and ${word%-*} to extract b and a respectively and do b-a+1 and add it with count calculated already and print the element after the loop
You can put this in a bash script with she-bang set to #!/bin/bash and run the script or run it directly from the command-line