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To store the output of a command as a variable in sh/ksh/bash, you can do either
var=$(command) or
var=`command` What's the difference if any between the two methods?
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$(...) allows command substitution, i.e. allows the output of a command to replace the command itself and can be nested.
Dollar sign $ (Variable) The dollar sign before the thing in parenthesis usually refers to a variable. This means that this command is either passing an argument to that variable from a bash script or is getting the value of that variable for something.
#$ does "nothing", as # is starting comment and everything behind it on the same line is ignored (with the notable exception of the "shebang"). $# prints the number of arguments passed to a shell script (like $* prints all arguments). Follow this answer to receive notifications. edited Jul 9 at 13:55.
A shell is a computer program that presents a command line interface which allows you to control your computer using commands entered with a keyboard instead of controlling graphical user interfaces (GUIs) with a mouse/keyboard/touchscreen combination.
The backticks/gravemarks have been deprecated in favor of $() for command substitution because $() can easily nest within itself as in $(echo foo$(echo bar)). There are other differences such as how backslashes are parsed in the backtick/gravemark version, etc.
See BashFAQ/082 for several reasons to always prefer the $(...) syntax.
Also see the POSIX spec for detailed information on the various differences.
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