CSV to JSON converter using BASH. Original script from http://blog.secaserver.com/2013/12/convert-csv-json-bash/

csv2json.sh

#!/bin/bash
# CSV to JSON converter using BASH
# original script from http://blog.secaserver.com/2013/12/convert-csv-json-bash/
# thanks SecaGuy!
# Usage ./csv2json.sh input.csv > output.json
 
input=$1
 
[ -z $1 ] && echo "No CSV input file specified" && exit 1
[ ! -e $input ] && echo "Unable to locate $1" && exit 1
 
read first_line < $input
a=0
headings=`echo $first_line | awk -F, {'print NF'}`
lines=`cat $input | wc -l`
while [ $a -lt $headings ]
do
        head_array[$a]=$(echo $first_line | awk -v x=$(($a + 1)) -F"," '{print $x}')
        a=$(($a+1))
done
 
c=0
echo "{"
while [ $c -lt $lines ]
do
        read each_line
        if [ $c -ne 0 ]; then
                d=0
                echo -n "{"
                while [ $d -lt $headings ]
                do
                        each_element=$(echo $each_line | awk -v y=$(($d + 1)) -F"," '{print $y}')
                        if [ $d -ne $(($headings-1)) ]; then
                                echo -n ${head_array[$d]}":"$each_element","
                        else
                                echo -n ${head_array[$d]}":"$each_element
                        fi
                        d=$(($d+1))
                done
                if [ $c -eq $(($lines-1)) ]; then
                        echo "}"
                else
                        echo "},"
                fi
        fi
        c=$(($c+1))
done < $input
echo "}"

Here's another version that works with Busybox, and does not rely on eval, altough using cut in order to find corresponding headers has a little performance impact.
Function should be highly portable

function CSV2JSON2 {
	local inputFile="${1}"				# Input csv text
	local separator="${2:-,}"			# Separator, defaults to ','
	
	local firstLine
	local lineCounter=0
	local numberOfHeadings=0
	local elementNumber=0
	local element
		
	while IFS= read -r line; do
		if [ "$line" == "" ] || [ "${line:0:1}" == "#" ]; then
			continue
		fi
		
		if [ $lineCounter -eq 0 ]; then
			numberOfHeadings=$(($(echo $line | grep -o "$separator" | wc -l)+1))
			firstLine="$line"
		else
			echo -e "\t\t{"
			elementNumber=1
			while [ $elementNumber -lt $numberOfHeadings ]; do
				headerElement="$(echo $firstLine | cut -d"$separator" -f$elementNumber)"
				element="$(echo $line | cut -d"$separator" -f$elementNumber)"

				if [ "$element" == "" ]; then
					element="null"
				fi
				
				echo -e "\t\t\"$headerElement\" : \"$element\","
				
				elementNumber=$((elementNumber+1))
			done
			
			echo -e "\t\t},"
		fi
		lineCounter=$((lineCounter+1))
	done < "$inputFile"
	# Add [ ] if more than one item in list
	if [ $lineCounter -gt 2 ]; then
		sed -i.tmp '1s/^/\t[\n/' "$outputFile"
		echo -e "\t]," >> "$outputFile"
	fi
}

Use with jsonOutput = "$(CSV2JSON2 "inputFile")"

@linosteenkamp's version does not work with CSV that contain quoted comma (",") e.g. printf "head1,head2,head3\n1,\"foo, bar, baz\",\"foo bar baz\"" | ./csv2json.sh will result in

[
        {
                "head1": 1,
                "head2": ""foo",
                "head3": " bar"
                "": " baz""
                "": "foo bar baz"
        }
]

Quick fix for @outwitevil's script (https://gist.github.com/dsliberty/3de707bc656cf757a0cb#gistcomment-2103308) is to replace the \r in the sed regex with $(printf '\r'). The script will still struggle with empty lines, so you have to delete them beforehand. A simple one-liner

printf "head1,head2,head3\n\n\n1,\"foo, bar, baz\",\"foo bar baz\"\n\n" | sed '/^[[:space:]]*$/d' | ./csv2json.sh

[
    {
        "head1": 1,
        "head2": "foo, bar, baz",
        "head3": "foo bar baz"
    }
]

I haven't checked if there are any side effects on Linux now.

#!/bin/bash

# CSV to JSON converter using BASH
# original script from https://gist.github.com/dsliberty/3de707bc656cf757a0cb
# Usage ./csv2json.sh input.csv > output.json
#       cat <input.csv> | csv2json > output.json
#set -x
shopt -s extglob

input="${1:-/dev/stdin}"

SEP=","

[ -z "${input}" ] && echo "No CSV input file specified" && exit 1
[ ! -e "${input}" ] && echo "Unable to locate ${input}" && exit 1

csv_nextField()
{
    local line="$(echo "${1}" | sed 's/$(printf '\r')//g')"
    local start=0
    local stop=0

    if [[ -z "${line}" ]]; then
        return 0
    fi

    local offset=0
    local inQuotes=0
    while [[ -n "${line}" ]]; do
        local char="${line:0:1}"
        line="${line:1}"

        if [[ "${char}" == "${SEP}" && ${inQuotes} -eq 0 ]]; then
            inQuotes=0
            break
        elif [[ "${char}" == '"' ]]; then
            if [[ ${inQuotes} -eq 1 ]]; then
                inQuotes=0
            else
                inQuotes=1
            fi
        else
            echo -n "${char}"
        fi
        offset=$(( ${offset} + 1 ))
    done

    echo ""
    return $(( ${offset} + 1 ))
}

read -r first_line < "${input}"
a=0
headings=$(echo "${first_line}" | awk -F"${SEP}" {'print NF'})

if [ "${input}" = "/dev/stdin" ]; then
  while read -r line
  do
    lines_str+="$line"$'\n'
    c=1
  done < "${input}"
else
  lines_str="$(cat "${input}")"
  c=0
fi

lines_num=$(echo "${lines_str}" | wc -l)

while [[ ${a} -lt ${headings} ]]; do
    field="$(csv_nextField "${first_line}")"
    first_line="${first_line:${?}}"
    head_array[${a}]="${field}"
    a=$(( ${a} + 1 ))
done

#c=0
echo "["
while [ ${c} -lt ${lines_num} ]
do
    read -r each_line
    each_line="$(echo "${each_line}" | sed 's/$(printf '\r')//g')"

    if [[ ${c} -eq 0 ]]; then
        c=$(( ${c} + 1 ))
    else
        d=0
        echo "    {"
        while [[ ${d} -lt ${headings} ]]; do
            item="$(csv_nextField "${each_line}")"
            each_line="${each_line:${?}}"
            echo -n "        \"${head_array[${d}]}\": "
            case "${item}" in
                "")
                    echo -n "null"
                    ;;
                null|true|false|\"*\"|+([0123456789]))
                    echo -n ${item}
                    ;;
                *)
                    echo -n "\"${item}\""
                    ;;
            esac
            d=$(( ${d} + 1 ))
            [[ ${d} -lt ${headings} ]] && echo "," || echo ""
        done

        echo -n "    }"

        c=$(( ${c} + 1 ))
        [[ ${c} -lt ${lines_num} ]] && echo "," || echo ""
    fi

done <<< "${lines_str}"
echo "]"

#!/bin/bash

CSV to JSON converter using BASH

Usage ./csv2json input.csv > output.json

input=$1
[ -z $1 ] && echo "No CSV input file specified" && exit 1
[ ! -e $input ] && echo "Unable to locate $1" && exit 1
read first_line < $input
a=0
headings=echo $first_line | awk -F, {'print NF'}
lines=cat $input | wc -l
while [ $a -lt $headings ]
do
head_array[$a]=$(echo $first_line | awk -v x=$(($a + 1)) -F"," '{print $x}' | tr -d '\r')
a=$(($a+1))
done
c=0
echo "["
while [ $c -le $lines ]
do
read each_line
if [ $c -ne 0 ]; then
d=0
echo -n "{"
while [ $d -lt $headings ]
do
each_element=$(echo $each_line | awk -v y=$(($d + 1)) -F"," '{print $y}' | tr -d '\r')
if [ $d -ne $(($headings-1)) ]; then
echo -n ""${head_array[$d]}":"$each_element","
else
echo -n ""${head_array[$d]}":"$each_element""
fi
d=$(($d+1))
done
if [ $c -eq $(($lines)) ]; then
echo "}"
else
echo "},"
fi
fi
c=$(($c+1))
done < $input
echo "]"

This should give with quatation and array of json objects

Question, the script runs fine but does not output a json file?

Problem if field value have more than 254 characters.After that field every other field will the same

I have a field that has the following value
"doc":0000000000000000000000000000000000000000000000000000000000000000,
what is interesting is that the all zeros is failing to be parsed by JSON tools ...

they either want a 0 or a "0000000000000000000000000000000000000000000000000000000000000000"

Is there a way that we can put quotes around all values even if they are numbers? or is that outside the accepted formatting of JSON?