[SOLVED] Functional Programming with Bash

Issue

How would I implement something similar to functional programming within bash?

I have a function:

requestPassword(){
    
    passwordValidated=false

    while [ "$passwordValidated" = "false" ];do
         tput clear
         [ -n "$infomsg" ] && echo -e "$infomsg" >&2
         [ -n "$errmsg" ] && echo -e "$errmsg" >&2
         read -s -p "some prompt:" pass >&2
         errmsg=$()#do some validation
         [ -n "$errmsg" ] && continue
         passwordValidated=true
    done
    echo "$pass"
}

But I want to make it as generic as possible to work with different systems

Maybe I want to ask the password for an encrypted file Maybe I want to ask the password for a system user Maybe I want to use this function to request a new password from a user

The idea would be that I could pass this function a function that takes in a pass parameter and only outputs something if validation failed

Solution

You can pass a function name as an argument

requestPassword(){
    local infomsg="$1"
    local validator=${2:-the_default_validator_function}
    # ...
    local errmsg
    errmsg=$( "$validator" "$pass" )
    # ...
}

then

# a valid "foobar" password contains the substring "foo"
foobarPasswordValidator() { [[ $1 == *foo* ]]; }

pass=$(requestPassword "Enter your FooBar password" foobarPasswordValidator) 

If you don't have a default validator, use : or true -- they accept arguments, ignore them(1) and return a "success" exit status.

---

(1) ignored after any parameter expansions have occurred

Answered By - glenn jackman

Answer Checked By - Gilberto Lyons (WPSolving Admin)