GNU Coding Standards
With occasional exceptions, utility programs and libraries for GNU should be upward compatible with those in Berkeley Unix, and upward compatible with ANSI C if ANSI C specifies their behavior, and upward compatible with POSIX if POSIX specifies their behavior.
When these standards conflict, it is useful to offer compatibility modes for each of them.
ANSI C and POSIX prohibit many kinds of extensions. Feel free
to make the extensions anyway, and include a `--ansi',
`--posix', or `--compatible' option to turn them off.
However, if the extension has a significant chance of breaking any real
programs or scripts, then it is not really upward compatible. Try to
redesign its interface.
Many GNU programs suppress extensions that conflict with POSIX if the
environment variable POSIXLY_CORRECT is defined (even if it is
defined with a null value). Please make your program recognize this
variable if appropriate.
When a feature is used only by users (not by programs or command
files), and it is done poorly in Unix, feel free to replace it
completely with something totally different and better. (For example,
vi is replaced with Emacs.) But it is nice to offer a compatible
feature as well. (There is a free vi clone, so we offer it.)
Additional useful features not in Berkeley Unix are welcome.
GNU Coding Standards
Packaging copyright © 1988-2000 OAR Corporation
Context copyright by each document's author. See Free Software Foundation for information.