Hello psy,

as you saw in the last post from Chubler and me, that we have different views on what is the preferred choice of coding. I hope this causes not too much confusion for you.

Global And Local Variables

I just checked your code at github and want to mention, that you are using global variables a lot which one should better avoid. Use local variables instead. A global variable is a variable that is accessible and changeable everywhere in the program. There's a danger if a global variable is changed/used where it is unexpected. One may use even the same variable name in different places for different purposes. It most likely will break the program. A local variable is valid only inside of a function in which it is defined.

Example:

Code:

# this is global
name="tony stark"

give_name() {

     # this is local
     local name="bruce banner"     # <--- this is the local variable name
                                   #      only valid in this function

     echo "$name"                  # <--- echo produces output of local variable name
}

give_name                          # <--- outputs what function give_name does ("bruce banner")

echo "hello $name"                 # <--- name is the global assigned name "tony stark"

name="$(give_name)"                # <--- assigns output of function 
                                   #      give_name()(="bruce banner") to global variable "name"

echo "hello $name"                 # <--- output newly assigned value of global variable

Output:

Code:

bruce banner
hello tony stark
hello bruce banner

Function Arguments And Return Values

A recommended way is to put what you need as arguments into your function and return back what you want from the function. Returning back in bash means mostly to print it(echo, printf, ...). (yes, return also exists, but I try to make it easy).

A simple example:

Code:

add() { 
   echo "$(( $1 + $2 ))"
}

sum="$( add "5" "4" )"

The function add takes 2 arguments, adds them and prints them. The output is received from the function and put into the (global) variable sum.

See also: Local Variables

P. S.: To avoid global variables is a good coding practice for starting. If one internalized it, one may break the habit occasionally.