Converting Values in a String Variable to Array in Shell Script [closed]

Generating the ranges and storing the dates in a bash array:

• First define a function that adds a month to a date:

next_month() {
    local y m
    IFS='-' read y m <<< "$1"
    if [ "$m" == 12 ]
    then
        m=1 y=$(( 10#$y + 1 ))
    else
        m=$(( 10#$m + 1 ))
    fi
    printf '%04d-%02d\n' "$y" "$m"
}

which can be trivial with GNU date:

next_month() { date -d "$1-01 +1month" '+%Y-%m'; }

or even BSD date

next_month() { date -j -v '+1m' -f '%Y-%m' "$1" '+%Y-%m'; }

• Then use it in the main loop that fills the array:

v="2020-01-2020-04,2020-11"

array=()
for date in ${v//,/ }
do
    [[ $date =~ ^([0-9]{4}-(0[1-9]|1[0-2]))(-([0-9]{4}-(0[1-9]|1[0-2])))?$ ]] || continue

    inidate=${BASH_REMATCH[1]}
    enddate=${BASH_REMATCH[4]:-$inidate}

    until [ "$inidate" == "$enddate" ]
    do
        array+=( "$inidate" )
        inidate=$(next_month "$inidate")
    done

    array+=( "$inidate" )
done

• And you'll get:

declare -p array
# declare -a array='([0]="2020-01" [1]="2020-02" [2]="2020-03" [3]="2020-04" [4]="2020-11")'

With bash, would you please try the following:

#!/bin/bash

v="2020-01-2020-04,2020-11"

IFS=, read -ra a <<< "$v"       # split $v on comma(s) into an array a
for i in "${a[@]}"; do
    if [[ $i =~ ^[0-9]{4}-[0-9]{2}$ ]]; then
        array+=("$i")           # single YYYY-MM
    elif [[ $i =~ ^([0-9]{4})-([0-9]{2})-([0-9]{4})-([0-9]{2})$ ]]; then
                                # range of two YYYY-MM's
        if (( 10#${BASH_REMATCH[1]} != 10#${BASH_REMATCH[3]} )); then
            echo "the range of year not supported."
            exit 1
        else
            for (( j = 10#${BASH_REMATCH[2]}; j <= ${BASH_REMATCH[4]}; j++ )); do
                                # expand the range of months
                array+=( "$(printf "%04d-%02d" $((10#${BASH_REMATCH[1]})) "$j")" )
            done
        fi
    fi
done

(IFS=","; echo "${array[*]}")   # print the result

Output:

2020-01,2020-02,2020-03,2020-04,2020-11