Count occurrences in a csv with Bash - bash

Question

I have to create a script that given a country and a sport you get the number of medalists and medals won after reading a csv file.
The csv is called "athletes.csv" and have this header
id|name|nationality|sex|date_of_birth|height|weight|sport|gold|silver|bronze|info
when you call the script you have to add the nationality and sport as parameters.
The script i have created is this one:
#!/bin/bash
participants=0
medals=0
while IFS=, read -ra array
do
if [[ "${array[2]}" == $1 && "${array[7]}" == $2 ]]
then
participants=$participants++
medals=$(($medals+${array[8]}+${array[9]}+${array[10]))
fi
done < athletes.csv
echo $participants
echo $medals
where array[3] is the nationality, array[8] is the sport and array[9] to [11] are the number of medals won.
When i run the script with the correct paramters I get 0 participants and 0 medals.
Could you help me to understand what I'm doing wrong?
Note I cannot use awk nor grep
Thanks in advance

Answer 1

Try this:
#! /bin/bash -p
nation_arg=$1
sport_arg=$2
declare -i participants=0
declare -i medals=0
declare -i line_num=0
while IFS=, read -r _ _ nation _ _ _ _ sport ngold nsilver nbronze _; do
(( ++line_num == 1 )) && continue # Skip the header
[[ $nation == "$nation_arg" && $sport == "$sport_arg" ]] || continue
participants+=1
medals+=ngold+nsilver+nbronze
done <athletes.csv
declare -p participants
declare -p medals
The code uses named variables instead of numbered positional parameters and array indexes to try to improve readability and maintainability.
Using declare -i means that strings assigned to the declared variables are treated as arithmetic expressions. That reduces clutter by avoiding the need for $(( ... )).
The code assumes that the field separator in the CSV file is ,, not | as in the header. If the separator is really |, replace IFS=, with IFS='|'.

Answer 2

I'm assuming that the field delimiter of your CSV file is a comma but you can set it to whatever character you need.
Here's a fixed version of your code:
#!/bin/bash
participants=0
medals=0
{
# skip the header
read
# process the records
while IFS=',' read -ra array
do
if [[ "${array[2]}" == $1 && "${array[7]}" == $2 ]]
then
(( participants++ ))
medals=$(( medals + array[8] + array[9] + array[10] ))
fi
done
} < athletes.csv
echo "$participants" "$medals"
remark: As $1 and $2 are left unquoted they are subject to glob matching (right side of [[ ... == ... ]]). For example you'll be able to show the total number of medals won by the US with:
./script.sh 'US' '*'
But I have to say, doing text processing with pure shell isn't considered a good practice; there exists dedicated tools for that. Here's an example with awk:
awk -v FS=',' -v country="$1" -v sport="$2" '
BEGIN {
participants = medals = 0
}
NR == 1 { next }
$3 == country && $8 == sport {
participants++
medals += $9 + $10 + $11
}
END { print participants, medals }
' athletes.csv
There's also a potential problem remaining: the CSV format might need a real CSV parser for reading it accurately. There exists a few awk libraries for that but IMHO it's simpler to use a CSV‑aware tool that provides the functionalities that you need.
Here's an example with Miller:
mlr --icsv --ifs=',' filter -s country="$1" -s sport="$2" '
begin {
#participants = 0;
#medals = 0;
}
$nationality == #country && $sport == #sport {
#participants += 1;
#medals += $gold + $silver + $bronze;
}
false;
end { print #participants, #medals; }
' athletes.csv