When you call a shell script from the command line, you can pass it additional arguments called Positional Parameters. For example, when entering the following in the command line to run the script myscript.sh:

./myscript.sh param1 param2

The variables would have the following values:

"$0" = "./myscript.sh"

"$1" = "param1"

"$2" = "param2"

The variable $# gives the number of parameters, not including the command. In this example:

"$#" = 2

The variable $* lists all the parameters as a single word (quotes added to emphasize string boundaries):

"$*" = "param1 param2"

The variable $@ lists each parameter as a separate quoted string (quotes added to emphasize string boundaries):

"$@" = "param1" "param2"

Note that you should almost always quote variables in bash, so you should use "$@" and not $@. See this programming guide for more information.