On May 28, 2020, at 12:23 AM, Paul Eggert <eggert@cs.ucla.edu> wrote:
That's not what the --version flag is for. --version is supposed to output the version number of the program, not of any data. This is the common meaning of "--version" across a wide variety of programs.
Yes. For example, the GNU coding standard says of --version: https://www.gnu.org/prep/standards/standards.html#g_t_002d_002dversion "The standard --version option should direct the program to print information about its name, version, origin and legal status, all on standard output, and then exit successfully."
zdump is intended to be portable to any system that conforms to POSIX, and since there's no POSIX-portable way to find out the tzdata version, zdump doesn't do that. There might not be any tzdata at all, and zdump is still supposed to work. Though perhaps this zdump design goal should change at some point....
And if there *were* a POSIX-portable way to find out the tzdata version, zdump should, *if* there's tzdata from which to find the version using the POSIX-portable way in question, have a *different* flag, e.g. --tzdata-version, to tell it to report that version.