Linux has some great built-in tools to help you how to use a command or check what flags are available for a command. One tool, help, is a built-in bash command that provides help for other bash commands (echo, logout, pwd, etc).
$ help echo
This will give you a description and the options you can use when you want to run echo. For other executable programs, it’s convention to have an option called --help or something similar.
$ echo --help
Not all developers who ship out executables will conform to this standard, but it’s probably your best shot to find some help on a program.
Run help on the echo command, logout command and pwd command.
How do you get quick command line help for built-in bash commands?