Question

I have a global variable

RT="\e[m"
TITLE="${FG}%s${RT}"

and have two functions

function one
{
   local FG="\e[33m"
   printf "$TITLE" "One"
}

function two
{
   local FG="\e[32m"
   printf "$TITLE" "Two"
}

but the color dont change, how to reuse the $TITLE variable

Answer 1

Short answer: you can’t, bash doesn’t have the equivalent of pointers. The variable $TITLE is assigned with the expansion of the rhs of the assignment character, so $TITLE has the value %s\e[m since $FG is not defined at expansion time, and hence expands to the empty string. As a work-around you could instead do:

rt=$'\e[m'
title="%s%s$rt"

one() {
    local fg=$'\e[33m'
    printf "$title" "$fg" "One"
}

two() {
    local fg=$'\e[32m'
    printf "$title" "$fg" "Two"
}

And using eval is not really a good option, as eval is evil!

I’ve also modified a few things from your script:

• Used lower case variable names (as using upper case variable names is considered bad practice in bash),
• Use $'...' to have the correct colors (instead of the strings "\e[m", …),
• Used the proper way to define functions in bash (without the keyword function).

Edit. From your comment, I see you’re really troubled with having to type "$fg" each time. So here’s another possibility: instead of defining a variable $title, define a function title that echos the formating string and use it like so:

rt=$'\e[m'

title() {
   echo "$fg%s$rt"
}

one() {
    local fg=$'\e[33m'
    printf "$(title)" "One"
}

two() {
    local fg=$'\e[32m'
    printf "$(title)" "Two"
}

Each time you call the function title, it echoes the formating string you need, hence $(title) will expand to that formating string. Each time you call the function title, the string "$fg%s$rt" is expanded, with whatever values the variables $fg and $rt have at this expansion time.