3

I'm on Mac and have just created an environment variable inside the .bash_profile directory, it works fine when I run:

$variable_name

I just want the know why the dollar sign is there and if it is possible to remove it. Any help would be appreciated :)

4

The $ (dollar sign) is there to reference variables in bash. You cannot remove it. Technically, it's called variable/parameter expansion. Basically the value of the variable is "expanded out".

Using variables in bash is pretty straight forward:

  • Don't use a "$" when setting a variable
  • Use the "$" when referencing/calling a variable

Example:

#!/bin/bash
var1=Hello
read var2
echo $var1 $var2
exit

In the above script, we set var1 to "Hello" and var2 to user input (assume "World"). The next command prints out the contents of both variables on a single line:

Hello World

For more details, it's best to start with a good tutorial: BASH Programming - Introduction HOW-TO. Also have a look at the Bash Reference Manual

Tip:

You can enclose the variable in braces - ${variable}. This serves to "protect" the variable from characters immediately following the variable name which would (incorrectly) become part of the variable

Example:

var1=foo
echo $var1bar
echo ${var1}bar

The first echo would produce nothing since the variable var1bar doesn't exist where as the second echo would produce the word foobar as expected. Personally, I use braces for all my variables as a matter of style.

  • 1
    Wow, thank you, great answer! I'll definitely read up some more :) – Charl Kruger May 8 '18 at 7:45

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