Password generators (Linux Bash, Windows PowerShell)

password-generator.ps1

# utility for password generator
function Get-RandomChar { 
    $length = $args[0]
    $characters = $args[1]
    $counter = 0
    $random = ""
    while($counter -ne $length) {
        $random += $characters.Substring((Get-Random -Maximum $characters.length), 1)
        $counter++
    }
    return $random 
}

# generate password
function Get-RandomPassword {
    $length = $args[0]
    # characters to work with
    $capitals = 'ABCDEFGHKLMNOPRSTUVWXYZ'
    $lowers = 'abcdefghiklmnoprstuvwxyz'
    $nums = '1234567890'
    $specials = '.!&=?@#+'

    # minimal length is 4
    if($length -lt 4) {$length = 4}

    # first 4 characters - required chars (capital, lower, number, special)
    $password = Get-RandomChar 1 $lowers
    $password += Get-RandomChar 1 $capitals
    $password += Get-RandomChar 1 $nums
    $password += Get-RandomChar 1 $specials

    # rest - only alphanumeric
    while($password.length -ne $length) {
        $password += Get-RandomChar 1 ($lowers + $capitals + $nums)
    }

    return $password;
}

# example
$new_password = Get-RandomPassword 10

password-generator.sh

#!/bin/bash

# utility for password generator
get_random_char () {
    if [ "$#" -ne 2 ]
    then
        echo "Usage: get_random_char [length] [characters]"
        exit 1
    fi

    length=$1
    characters=$2
    if [[ length -lt 1 ]]; then length=1; fi
    charactersLength=${#characters}
    if [[ charactersLength -lt 1 ]]; then characters="*"; charactersLength=1; fi

    random_chars=""
    
    for ((n=0;n<$length;n++))
    do
        rand=$((0 + $RANDOM % charactersLength))
        random_chars+=${characters:rand:1}
    done

    echo $random_chars    
}

# generate password
generate_password () {
    if [ "$#" -ne 1 ]
    then
        echo "Usage: generate_password [length]"
        exit 1
    fi
    length=$1

    # minimal length is 4
    if [[ length -lt 1 ]]; then length=4; fi

    # characters to work with
    capitals='ABCDEFGHKLMNOPRSTUVWXYZ'
    lowers='abcdefghiklmnoprstuvwxyz'
    nums='1234567890'
    specials='.!&=?@#+'

    # first 4 characters - required chars (capital, lower, number, special)
    password="$(get_random_char 1 $lowers)"
    # echo $password
    password+="$(get_random_char 1 $capitals)"
    # echo $password
    password+="$(get_random_char 1 $nums)"
    # echo $password
    password+="$(get_random_char 1 $specials)"
    # echo $password

    # rest - only alphanumeric
    for ((n=4;n<$length;n++))
    do
        password+="$(get_random_char 1 "${lowers}${capitals}${nums}")"
        # echo $password
    done

    echo $password
}

# example
new_pass=$(generate_password 10)