appending a variable to a file in Bash not working

Question

I have a code like this

#! /bin/bash

$version = "1.0";
$preffix = "ApplicationName.";

for f in pack*;
do
    echo "bla bla bla" > myFile.txt
    echo $preffix >> myFile.txt
    echo "more stuff" >> myFile.txt
    echo $version >> myFile.txt
done;

the output is

bla bla bla

more stuff

$version and $preffix are not added to myFile.txt... why?

Answer 1

This program will work where yours doesn't:

#!/bin/bash

version="1.0";
preffix="ApplicationName.";

for f in pack*;
do
    echo "bla bla bla" > myFile.txt
    echo $preffix >> myFile.txt
    echo "more stuff" >> myFile.txt
    echo $version >> myFile.txt
done;

Your affection for spaces makes your program more readable, and also makes it not work.

Also, while it doesn't matter for this program, it would be a really good idea to do this:

#!/bin/bash

version="1.0";
preffix="ApplicationName.";

for f in pack*;
do
    echo "bla bla bla" > myFile.txt
    echo "$preffix" >> myFile.txt
    echo "more stuff" >> myFile.txt
    echo "$version" >> myFile.txt
done;

This is because if you did something like:

version='1  2'

in your original program, you would end up with a somewhat unexpected result. Putting the quotes around your variables is a really good idea to prevent mysterious errors like that.

Answer 2

The $ sign in front of variables is used to read them.

If you want to assign them, you have to leave out the $ sign, i.e.:

version="1.0"
preffix="ApplicationName."

Also, the ; are not required at the end of the assignment lines.