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From: Douglas McIlroy <>
To: The Eunuchs Hysterical Society <>
Subject: Re: [TUHS] Systematic approach to command-line interfaces [ meta issues ]
Date: Sun, 1 Aug 2021 14:17:39 -0400	[thread overview]
Message-ID: <> (raw)

I have considerable sympathy with the general idea of formally
specifying and parsing inputs. Langsec people make a strong case
for doing so. The white paper,"A systematic approach to modern
Unix-like command interfaces", proposes to "simplify parsing by
facilitating the creation of easy-to-use 'grammar-based' parsers".

I'm not clear on what is meant by "parser". A plain parser is a
beast that builds a parse tree according to a grammar. For most
standard Unix programs, the parse tree has two kinds of leaves:
non-options and options with k parameters. Getopt restricts
k to {0,1}.

Aside from fiddling with argc and argv, I see little difference
in working with a parse tree for arguments that could be
handled by getopt and working with using getopt directly.

A more general parser could handle more elaborate grammatic
constraints on options, for example, field specs in sort(1),
requirements on presence of options in tar(1), or representation
of multiple parameters in cut(1).

In realizing the white paper's desire to "have the parser
provide the results to the program", it's likely that the mechanism
will, like Yacc, go beyond parsing and invoke semantic actions
as it identifies tree nodes.

Pioneer Yaccification of some commands might be a worthy demo.


             reply	other threads:[~2021-08-01 18:18 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-01 18:17 Douglas McIlroy [this message]
2021-08-01 19:48 ` arnold
2021-08-01 21:30   ` John Cowan
2021-08-02 12:11   ` Steffen Nurpmeso
  -- strict thread matches above, loose matches on Subject: below --
2021-07-31 12:25 [TUHS] Systematic approach to command-line interfaces Michael Siegel
2021-07-31 19:20 ` [TUHS] Systematic approach to command-line interfaces [ meta issues ] Jon Steinhart
2021-07-31 21:06   ` Richard Salz
2021-07-31 21:32     ` Jon Steinhart
2021-07-31 21:37       ` Richard Salz
2021-07-31 21:55         ` Jon Steinhart
2021-07-31 22:10       ` Warner Losh
2021-07-31 22:19         ` Larry McVoy
2021-07-31 22:20         ` Jon Steinhart
2021-07-31 23:26           ` Warner Losh
2021-07-31 23:41             ` Jon Steinhart
2021-07-31 22:04   ` Bakul Shah
2021-07-31 22:13     ` Larry McVoy
2021-07-31 22:14       ` Bakul Shah
2021-07-31 22:17         ` Bakul Shah
2021-07-31 22:16     ` Jon Steinhart
2021-07-31 22:20       ` Bakul Shah

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