Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!mcsun!ukc!edcastle!yfcw14
From: yfcw14@castle.ed.ac.uk (K P Donnelly)
Newsgroups: comp.lang.fortran
Subject: Re: Command line arguements?
Message-ID: <10756@castle.ed.ac.uk>
Date: 2 Jun 91 16:32:16 GMT
References: <1991May31.234623.7735@murdoch.acc.Virginia.EDU> <24885@lanl.gov>
Organization: Edinburgh University
Lines: 52

Here is my explanation for the trouble writing a program on Unix which
acquires parameters from the command line but which doesn't need ugly
quoting to stop the shell trying to do wildcarding on filenames:-

Standard Unix does not have dynamic loading or shareable libraries or
whatever you want to call it.  So standard Unix does not have a
"parameter acquisition mechanism" usable by all commands.  Without
shareable libraries, a parameter acquisition mechanism would probably
add 100K or more to the size of every executable.

One consequence of this is that every Unix command has its own command
line syntax.  There is very little consistency between commands, and
most of them have a very primitive and non robust method of parameter
acquisition (or "option" acquisition, since most parameters are called
"options" on Unix).

Another consequence is that commands depend on the shell to do an
extremely primitive form of command line parsing.  The shell knows
nothing about the kind of parameters the command is expecting, so the
kinds of things it does to the command line may be completely inappropriate.
This is what is happening in the
            phone sm*th*
example.  The shell doesn't whether or not the "phone" command is
expecting a filename parameter, so it just goes ahead and assumes that
it is anyway.

Contrast with this Edinburgh University's own operating system, EMAS,
which has had dynamic linking at for a decade or more.  It has
a "parameter aquisition mechanism" (PAM) which all commands make use of.
It is linked in at load time so it doesn't add to the size of executables.
Commands like "cp" would tell PAM that they were expecting filename
parameters - in fact possibly too filenames which which agree in their
wildcarding, so
            cp dir1/* dir2/*
would copy all files from directory dir1 to dir2.  Commands like "phone"
would not tell PAM that they were expecting a filename parameter, so
"sm*th*" would not be interpreted as a set of filenames.  No cumbersome
quoting is necessary to switch off such interpretation.  As well as
that, parameter acquisition is much more user friendly.  If the
parameter is not of the type expected (e.g. a filename which is exists
and is readable) then PAM issues a meaningful error message and
reprompts the user for the parameter.

Unfortunately Edinburgh University's EMAS operating system is
disappearing exactly one year from now.  They are moving over to Unix to
be the same as everyone else.

Does anyone know whether any kind of user friendly parameter acquisition
mechanism is available for versions of Unix like SunOS which do have
shareable libraries?

   Kevin Donnelly