Consistently Inconsistent 27OPTIONS. (“Cat came back from Berkeley waving flags,” in the
words of Rob Pike, perhaps the ultimate Unix minimalist.)This philosophy, in the hands of amateurs, leads to inexplicably
mind-numbing botches like the existence of two programs, “head”
and “tail,” which print the first part or the last part of a file, depend-
ing. Even though their operations are duals of one another, “head”
and “tail” are different programs, written by different authors, and
take different options!If only the laws of thermodynamics were operating here, then Unix would
have the same lack of consistency and entropy as other systems that were
accreted over time, and be no better or worse than them. However, archi-
tectural flaws increase the chaos and surprise factor. In particular, pro-
grams are not allowed to see the command line that invoked them, lest they
spontaneously combust. The shell acts as an intermediary that sanitizes and
synthesizes a command line for a program from the user’s typing. Unfortu-
nately, the shell acts more like Inspector Clouseau than Florence Nightin-
gale.
We mentioned that the shell performs wildcard expansion, that is, it
replaces the star () with a listing of all the files in a directory. This is flaw
#1; the program should be calling a library to perform wildcard expansion.
By convention, programs accept their options as their first argument, usu-
ally preceded by a dash (–). This is flaw #2. Options (switches) and other
arguments should be separate entities, as they are on VMS, DOS, Genera,
and many other operationg systems. Finally, Unix filenames can contain
most characters, including nonprinting ones. This is flaw #3. These archi-
tectural choices interact badly. The shell lists files alphabetically when
expanding “”, and the dash (-) comes first in the lexicographic caste sys-
tem. Therefore, filenames that begin with a dash (-) appear first when “*”
is used. These filenames become options to the invoked program, yielding
unpredictable, surprising, and dangerous behavior.
Date: Wed, 10 Jan 90 10:40 CST
From: [email protected] (Kees Goossens)
Subject: Re: rm *
Newsgroups: alt.folklore.computers(^6) Using “cat” to type files to your terminal is taking advantage of one of its side
effects, not using the program for its “true purpose.”