command line, command-line

Two words as a noun. Hyphenate as an adjective.

Examples
command-line parameter
command-line tool

Customers enter commands at a command prompt, not on a command line.

It's OK to use on the command line in the context of building apps using command-line tools in Visual Studio.

Use command-line program in content for a general audience. Use console application only in content for a technical audience.

See also
Formatting developer text elements
command prompt
console