Flags

[Petrolhead]

Hi,

why do some man pages recommend using the -- before string flags?
javac -classpath
seems to work fine..

[jim mcnamara]

Because some few options start with the same single character as string options

-f
--foo

and the commandline interpreter will find -f and -foo to be the same thing.

[Petrolhead]

Thanks.. that explains it

[bwkaz]

It actually depends on whether the program uses getopt, getopt_long, getopt_long_only, or its own homegrown routine to parse its command line.

getopt only recognizes single-character options, like -f.

getopt_long recognizes both single-character options, like -f, and their equivalent long versions, like --foo. When the program uses getopt_long, -foo parses as "the -f option, with argument oo".

getopt_long_only doesn't recognize short options at all. -foo and --foo are the same to it.

If the argument-parsing routine is homegrown, then anything goes.

I would actually guess, given the way that Sun does the rest of their JDK (and the fact that a JDK is required to compile the JDK...), that their argument parsing is homegrown. But that's only a guess.

FWIW, most of the X toolkit arguments are single-dash as well (-display is probably the most common, followed by -geometry). I think Xlib uses a homegrown routine as well.