How to concatenate string variables in Bash

Question

In PHP, strings are concatenated together as follows:

$foo = \"Hello\";
$foo .= \" World\";

Here, $foo becomes \"Hello World\"

Answer 1

bla=hello
laber=kthx
echo "${bla}ohai${laber}bye"

Will output

helloohaikthxbye

This is useful when $blaohai leads to a variable not found error. Or if you have spaces or other special characters in your strings. "${foo}" properly escapes anything you put into it.