Menu
The system shell prompt That dollar sign means: we're in the system shell, i.e the program that you're put into as soon as you open the Terminal app. The dollar sign is often the symbol used to signify where you can begin typing in commands (you should see a blinking cursor there).
$- prints The current set of options in your current shell. himBH means following options are enabled: H - histexpand : when history expansion is enabled. m - monitor : when job control is enabled.
$1 means an input argument and -z means non-defined or empty. You're testing whether an input argument to the script was defined when running the script. Follow this answer to receive notifications.
Usage of the $ like ${HOME} gives the value of HOME. Usage of the $ like $(echo foo) means run whatever is inside the parentheses in a subshell and return that as the value. In my example, you would get foo since echo will write foo to standard out
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"Could anybody help me to figure out how this command get executed?
Let's look at different parts of the command. BASH_SOURCE is a bash array variable containing source filenames. So "${BASH_SOURCE[0]}" would return you the name of the script file.
dirname is a utility provided by GNU coreutils that remove the last component from the filename. Thus if you execute your script by saying bash foo, "$( dirname "${BASH_SOURCE[0]}" )" would return .. If you said bash ../foo, it'd return ..; for bash /some/path/foo it'd return /some/path.
Finally, the entire command "$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )" gets the absolute directory containing the script being invoked.
$(...) allows command substitution, i.e. allows the output of a command to replace the command itself and can be nested.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With