3.1. Variables
I'm not going to try to explain all the details of Bash scripting in a
section of this HOWTO, just the details pertaining to prompts. If you want
to know more about shell programming and Bash in general, I highly
recommend Learning the Bash Shell by Cameron Newham
and Bill Rosenblatt (O'Reilly, 1998). Oddly, my copy of this book is quite
frayed. Again, I'm going to assume that you know a fair bit about Bash
already. You can skip this section if you're only looking for the basics,
but remember it and refer back if you proceed much farther.
Variables in Bash are assigned much as they are in any programming
language:
testvar=5
foo=zen
bar="bash prompt" |
Quotes are only needed in an assignment if a space (or special character,
discussed shortly) is a part of the variable.
Variables are referenced slightly differently than they are assigned:
> echo $testvar
5
> echo $foo
zen
> echo ${bar}
bash prompt
> echo $NotAssigned
> |
A variable can be referred to as $bar or
${bar}. The braces are useful when it is unclear what
is being referenced: if I write $barley do I mean
${bar}ley or ${barley}? Note also
that referencing a value that hasn't been assigned doesn't generate an
error, instead returning nothing.