Why do Command Line flags like --recursive have two dashes instead of just -recursive?
I know that the shortened version is just -r.
Why do these flags use two hyphens rather than one hyphen?
Is there a maximum number of characters that a flag with one dash can have before it requires two dashes?
The issue is that you can say things like ls -laR;
it’s equivalent to ls -l -a -R.
So -recursive would be interpreted as -r -e -c -u -r -s -i -v -e.
There's no exact rule to use single or double dash as an option to a program. If one decided to handle options on one's own one can implement whatever one want.
But if programmer isn't looking for a PITA and want the program to use common, well recognizable way then one would use standard function(s) getopt/getopt_long that handle long options (long string as you asked) as double dashed an short options(single character) prefixed with single dash. The function getopt is part of <unistd.h> in C language. The same function can be used on Unix based systems in standard shells man getopt 1 that utilize parsing single and double dashed (long) options.
Is there a maximum number of characters that a flag with one dash can have before it requires two dashes?
If one uses function described above then short options can have only one single character.
