CODEWITHSUNDEEP
bashshellscripting
Danut Chirila
Danut Chirila

Reputation: 45

bash getting numbers from a file and make the average of them

Write a script that expects a file as its first argument. Some lines of the file will consist of integers 0 - 1000. The script should select the lines matching the previous criteria and print out their average to stdout (average of n integers is their sum divided by n).

And the file given looks like this:

22
78907
77 88 99 0000
need 11 gallons of water
0
roses are red
11

Example output:

11

Explanation: (22 + 11 + 0) / 3 = 11

I have tried already with this code:

#!/bin/bash

sum=0
ind=0

while IFS='' read -r line || [[ -n "$line" ]]; do
   if [[ $line =~ ^[a-zA-Z\ ]+$ ]]
   then
        ${sum}=${sum}+${#line} 
        ${ind}=${ind}+1 
        echo ${sum}
   fi        
done < "$1"

value=${sum}/${ind}
echo ${value}

the print of this code is always 0/0 and some errors like:

./test1: line 9: 0=0+13: command not found
./test1: line 10: 0=0+1: command not found

Any ideas?

Upvotes: 1

Views: 1306

Answers (1)

ghoti
ghoti

Reputation: 46896

Part of the issue with your script is answered here.. Your variable assignments are incorrect. You only use the $ to refer to a variable that has already been assigned. The assignment process drops the dollar sign.

The other issue you're having is that your arithmetic is not being expressed within an arithmetic expression.

Note that you can use use arithmetic expansion to handle your variables:

  if [[ $line =~ ^[a-zA-Z\ ]+$ ]]; then
      (( sum += ${#line} ))
      (( ind++ ))
      printf '%s\n' "$sum"
  fi

and later ...

value="$(( sum / ind ))"
printf '%s\n' "$value"

Beware that bash can only deal with integer math, floats are truncated. For more advanced math, consider using bc or dc (which are not built in to bash, they are separate tools that may need to be installed on your system) or another language like awk or perl which can do the same thing with better performance and more precise math.

That said, you can "fake" a couple of decimal places with a few extra lines of code and string manipulation, if you really need to:

$ sum=100; ind=7
$ printf -v x '%d' "$((${sum}00/${ind}))"
$ printf '%d.%d\n' "${x%??}" "${x:$((${#x}-2))}"
14.28

The first printf has division which multiplies the dividend by 100 (by adding two zeroes after it). The resultant quotient is then split with the second printf to insert the decimal point. This is a hack. Use tools that support real math.

Upvotes: 2

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