I am hearing these two terms interchangeably and I am wondering if there is any difference between them, like flags are for one letter options or flags are after a single dash.
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19
You'll probably find "arguments", "options", and "switches" are also often used interchangeably in this context as well.
"Flags" specifically, are Boolean arguments, set by the mere inclusion of the command-line argument, with no additional data needed or allowed for the argument. If you include the argument/option/flag, it counts as "true" and if you exclude it, it counts as "false".
Example Flag-type argument:
command.exe -DeleteFiles
Example of non-flag argument:
command.exe -ServerName my.server.com
Ƭᴇcʜιᴇ007
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According to Build Awesome Command-Line Applications in Ruby 2 the main distinction is: a switch doesn't take arguments, while a flag does. Quoting directly from the book (page 15):
Typically, if a switch is in the long-form (for example --foo), which turns “on” some behavior, there is also another switch preceded with no- (for example --no-foo) that turns “off” the behavior.
Finally, long-form flags take their argument via an equal sign, whereas in the short form of a flag, an equal sign is typically not used. For example, the curl command, which makes HTTP requests, provides both short-form and long-form flags to specify an HTTP request method: -X and --request, respectively. The following example invocations show how to properly pass arguments to those flags:
curl -X POST http://www.google.com
curl --request=POST http://www.google.com
