On Thu, Mar 5, 2020, 02:16 Quentin Rameau <quinq@fifth.space> wrote: > > On Thu, 5 Mar 2020 01:42:37 -0800 > Michael Forney <mfor...@mforney.org> wrote: > > > >> and `-d""` is invalid, since paste(1) must follow the > > >> utility syntax guidelines (guideline 7). > > > > > > Not sure what you mean there, -d"" is the concatenation of -d and > > > '', which is standard. > > > Did you quote the correct guideline? “Guideline 7: Option-arguments > > > should not be optional.” here there's an option-argument, that's an > > > empty string. > > > > I guess it's a combination of 6 and 7. Option arguments must be > > separate parameters and non-optional (unless specified otherwise). > > There is an exception made that allows conforming implementations to > > accept an option adjacent with its option argument in the same > > argument, but I think this only makes sense if the option-argument is > > non-empty. > > > > POSIX says > > > > The construct '\0' is used to mean "no separator" because historical > > versions of paste did not follow the syntax guidelines, and the > > command: > > > > paste -d"" ... > > > > could not be handled properly by getopt(). > > > > I think this implies that `paste -d""` is no longer valid, due to the > > requirements of the syntax guidelines. > > Rather it's due to a getopt() limitation with the (not so) special case > of an empty string option-argument, but I'm not sure why.
This has nothing to do with getopt(). This is about how the shell parses and splits words into arguments. -d"" is exactly the same as -d. It is the same word, adding an empty string to the end of a string does not change that original string. There is no argument to -d there. If you wanted to -d"" to pass two arguments "-d" and "" then you'd have to write a new shell to do that. As it stands shells pass on "-d" in argv when they come across -d"".
