Wsrtjtyk

given an input file with data like this:

id,name

10,abc

20,xyz

30,def

I am trying to sum the values in the id column.

Note: the reason I am using awk -v header is because I have multiple files all of which have id as a common header name but at different positions.

The output I am expecting is the total sum of id (i.e., for the example above the output is 60).

The code below works and returns the expected output, but I have to create a temp file in the code and then calculate the sum.

I tried many variations unfortunately all my efforts failed.

I want to avoid writing the data to a temp file, intfile.txt, but I am stuck.

Any solutions/suggestions appreciated.

ps: I am relatively new to shell scripting and I know code is not written well, but I am working through it.

#!/bin/bash

awk -v header="id" '

BEGIN { FS=","; a=0 }

NR == 1 { for (i=1;i<=NF;i++) { if ($i==header) { a=i }} }

a=NR > 1 && a>0 { print $a }' testfile.txt>intfile.txt

awk '{s+=$1}END{print s}' intfile.txt

#!/usr/bin/env bash



target="id"   # the field you want to sum

target_idx=   # the column number of that field

sum=0         # the sum that was found so far



{

  # first, just read the header...

  IFS=, read -r -a header

  for idx in "${!header[@]}"; do  # and look for the target field in it

    [[ ${header[$idx]} = $target ]] && { target_idx=$idx; break; }

  done

  [[ $target_idx ]] || { echo "ERROR: No $target field found" >&2; exit 1; }



  # then, iterate over other lines

  while IFS=, read -r -a line; do

    sum=$(( sum + ${line[$target_idx]} ))

  done

} <testfile.txt



echo "$sum"

See this running at https://ideone.com/MOnpFM

Some references:

• The basics of reading a file line-by-line by calling read repeatedly are covered in BashFAQ #1.


• Fancy array syntax (including the parameter expansion "${!array[@]}" to iterate over indices) is covered in the bash-hackers' page on arrays, BashFAQ #5, and also the BashGuide array page.


• Arithmetic syntax ($(( ... )) for math) is covered in the bash-hackers' wiki at http://wiki.bash-hackers.org/syntax/arith_expr
  

Try this also:

idline=$(grep id input.txt)

IFS=',' read -ra elem <<< "$idline"

idfld=0

for i in "${elem[@]}"; do

    idfld=$(($idfld+1))

    if [[ "$i" = "id" ]]

    then

        break;

    fi

done

gt=0

for num in `cat input.txt|grep "^[0-9]"|cut -d"," -f${idfld}`; do

    gt=$(($gt+$num ))

done

echo $gt