Shell Programming and Scripting

I have 2 variables in my shell scripts in which i am using awk and calculating 2 files and getting 2 different variable called in_total and out_total. I want to subtract one variable from another so plz tell me how i can do that.

Example is:

cat in_file | awk -F: '{
in_total += $1 * 86400 + $2 * 3600 + $3 * 60 + $4
}'

cat out_file | awk -F: '{
out_total += $1 * 86400 + $2 * 3600 + $3 * 60 + $4
}'

so plz tell me how i can subtract out_total from in_total

You don't need cat.

Code:

awk -F: '{
  FILENAME=="in_file" {in_total += $1 * 86400 + $2 * 3600 + $3 * 60 + $4}
  FILENAME=="out_file" {out_total += $1 * 86400 + $2 * 3600 + $3 * 60 + $4 }
  END { printf("%f\n", in_total - out_total) }
}' in_file out_file

I know there are many similar questions but have not been able to find a syntax in the posts that work.

I calculate var1 and var2 in a previous portion of the script. Then i want to set var3 to var2-var1.
Have tried all kinds of variations on:

var3 = `"expr $var2 - $var1`

I'm unfortunately not exactly a unix newbie, just not a natural

thanks for any help.

-dharol

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Code:

@ var3 = $var2 - $var1

In a real scripting shell, use:

Code:

var3=$(( $var2 - $var1 ))