On Tue, May 03, 2005 at 10:26:45AM -0400, Larry Jones wrote: > Keith MARSHALL writes: > > > > Really? I didn't know that, sorry. I used `type' to check that all of the > > necessary prerequisite programs are installed, because I understood that it > > *was* standard in Bourne shell; I've never come across one that didn't have > > it, but my experience has been exclusively with System V, (since SVR2), and > > more recently with GNU/Linux. > > To my knowledge, it has *never* been in the Bourne shell, it is the Korn > shell's (ksh) answer to the C shell's "which" command. On SysV, it is > fairly common to have sh be a link to ksh rather than being the real > Bourne shell (that's how David Korn "proved" that ksh was completely > upward compatible with sh -- he replaced sh with ksh on many of AT&T's > systems and no one noticed), which is probably the source of your > confusion.
Well, like it or not, Korn shell was the basis for POSIX. :-) I personally like that. For what it's worth, type is just an alias for whence -v in Korn shell. See below for portable way to do this. > > I followed the portability guidelines in the > > Autoconf documentation, which does not list `type' as a non-portable Bourne > > shell builtin, (in the `info' for 2.59) :-( > > Probably for the same reason it doesn't list "foobar" as a non-portable > Bourne shell builtin. :-) The current more-or-less definitive > specification of the shell command language is that specified by the > Single UNIX Specification/POSIX: > > > <http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html> > > The built-ins are on a separate page: > > <http://www.opengroup.org/onlinepubs/009695399/idx/sbi.html> > > > 3) For each test currently implemented using `type', reproduce the program > > file location strategy used by Autoconf; this is likely to result in the > > most portable solution, but is rather long winded. > > > > 4) Implement `type' as a shell function, based on the Autoconf strategy, > > within `pdfroff.sh'; this would appear to be the most attractive option, > > *but* the Autoconf documentation says not to use shell functions. > > I agree with your analysis. For what it's worth, CVS (which is also GNU > software and widely portable) has the same problem in its test suite > (although not in the core product) and uses a shell function to solve > it. In fact, the test suite makes extensive use of shell functions. So > I suggest going with 4: it's inifinitely better than using "type" and it > seems to be "portable enough". No need for the shell function. POSIX specifies this: The command -v and -V options were added to satisfy requirements from users that are currently accomplished by three different historical utilities: type in the System V shell, whence in the KornShell, and which in the C shell. Since there is no historical agreement on how and what to accomplish here, the POSIX command utility was enhanced and the historical utilities were left unmodified. The C shell which merely conducts a path search. The KornShell whence is more elaborate-in addition to the categories required by POSIX, it also reports on tracked aliases, exported aliases, and undefined functions. So the solution is to use command -v. All the best. Zvezdan Petkovic _______________________________________________ Groff mailing list Groff@gnu.org http://lists.gnu.org/mailman/listinfo/groff
