Using a variable's value to use that variables value

Question

Alright, so I'm trying to use a variables value to then use the value of that variable inorder to get the value of that variable.

So, my script takes $1 as a message, and then takes $2 as the color in which to print that out as.

#!/bin/bash

# TAKES $1 as MSG and $2 as COLOR.
export black='echo -e "\E[30;47m"'
export red='echo -e "\E[31;47m"'
export green='echo -e "\E[32;47m"'
export yellow='echo -e "\E[33;47m"'
export blue='echo -e "\E[34;47m"'
export magenta='echo -e "\E[35;47m"'
export cyan='echo -e "\E[36;47m"'
export white='echo -e "\E[37;47m"'

# VARIABLES
export color="$2"              # Set Color
export message="$1"            # Set MSG

# Use $color for what variable to substitute with, so we get the echos.
# Previously tried \$$color to get $whatever_$2_was but it wouldn't get the value.
\$$color

echo "$message"                # Echo Message.
tput sgr0                      # Reset to normal.

It'd be called as:

USAGE: cecho "MESSAGE" color

So, basically the scripts point is to color $message with whatever $2 equals.

Anyidea how to either:

1. Get the value of the variable with the $2 name,

or

2. Better way of writing this script?

Jonathan Leffler · Accepted Answer · 2013-08-29 00:58:12Z

5

Look up indirection (fourth paragraph of Shell Parameter Expansion):

${!color}

If color=white, this will generate the string from $white, which is what you're after, I think. You could also look up the eval command, but it is generally not as desirable (more dangerous than) the ${!color} notation.

As to better ways to write the script: I'd defer the echo -e until I used the colours, and I wouldn't export the variables unless you're planning to dot (.) or source the script:

black='\E[30;47m'
...
white='\E[37;47m'

...
color="$2"
...

echo -e "${!color}"

edited Aug 29, 2013 at 0:58

answered Aug 29, 2013 at 0:53

Jonathan Leffler

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1 Comment

Jared Allard Over a year ago

Exactly what I was looking for and Worked amazingly, thanks for the solution and the tips!

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