How to check if string is present in bash array using awk-CodePudding

I've got a file that looks like this:

a    12345
b    3456
c    45678

and i've got bash array of strings:

mylist=("a" "b")

What I want to do is to sum numbers in second column but only for rows where first column value (aka "a" or "b") is present in mylist.

My not-working code:

cat myfile.txt | awk -F'\t' '{BEGIN{sum=0} {if ($1 in ${mylist[@]}) sum =$2} END{print sum}}'

Expected result is 12345 3456=15801. I understand that problem is in if-statement but can't figure out how to rearrange this code to work.

CodePudding user response：

Doing it in pure bash by making the elements of the original array keys in an associative one:

#!/usr/bin/env bash

mylist=(a b)

# Use the elements of the array as the keys in an associative array
declare -A keys
for elem in "${mylist[@]}"; do
    keys[$elem]=1
done


declare -i sum=0
# Read the lines on standard input
# For example, ./sum.sh < input.txt
while read -r name num; do
    # If the name is a key in the associative array, add to the sum
    if [[ -v keys[$name] ]]; then
        sum =$num
    fi
done

printf "%d\n" "$sum"

CodePudding user response：

There's no good reason to make awk read the array in the first place. Let join quickly pick out the matching lines -- that's what it's specialized to do.

And if in real life your array and input file keys are guaranteed to be sorted as they are in the example, you can take the sort uses out of the code below.

# Cautious code that doesn't assume input sort order
LC_ALL=C join -1 1 -2 1 -o1.2 \
  <(LC_ALL=C sort <myfile.txt) \
  <(printf '%s\n' "${mylist[@]}" | LC_ALL=C sort) \
  | awk '{ sum  = $1 } END { print sum }'

...or...

# Fast code that requires both the array and the file to be pre-sorted
join -1 1 -2 1 -o1.2 myfile.txt <(printf '%s\n' "${mylist[@]}") \
  | awk '{ sum  = $1 } END { print sum }'

CodePudding user response：

One method would be:

#!/bin/bash

mylist=(a b)

awk '
    FNR==NR { a[$1]; next }
    $1 in a { sum  = $2 }
        END { print sum }
' <(printf '%s\n' "${mylist[@]}") file

Note that, when initializing an array in bash, array elements are separated by whitespaces, not commas.