Without any options, the julia command starts up the REPL environment. A useful option to check your environment is julia -v. This shows Julia's version, for example, julia version 1.0.0. (The versioninfo()function in REPL is more detailed, and the VERSION constant only gives you the version number: v"1.0.0"). An option that lets you evaluate expressions on the command line itself is -e, for example:
julia -e 'a = 6 * 7;println(a)'
The preceding commands print out 42 (this also works in a PowerShell window on Windows, but in an ordinary Windows Command Prompt, use " instead of the ' character).
Some other options that are useful for parallel processing will be discussed in Chapter 9, Running External Programs ...