jkcohen@udenva.UUCP (08/22/84)
CRITIQUE
of the
BERKELEY 4.2 UNIX DOCUMENTATION - Volume IIc
Sections 39-40
by
Jack K. Cohen
August 21, 1984
Copyright 1984 by Jack K. Cohen
Permission to copy all or part of this material is granted
provided that the copies are not made or distributed for
direct commercial advantage, the author's copyright notice
and the title of the article and its date appear, and notice
is given that copying is by permission of the author. To
copy otherwise, or to republish, requires a fee and/or
specific permission.
4.2BSD -1-
Introduction
I am hoping to issue a set of mini-critiques of the
Programmer's Manual Volume IIc to supplement the Critique of
Volume I which was recently distributed. This first
installement covers the first two sections of Volume IIc.
There are many sections totally beyond my interests and
abilities, but in addition to sections 39 and 40 presented
here, I anticipate eventually covering at least sections 41,
43, 45, 53, 54, and 56.
J. K. Cohen
4.2BSD -2-
Bug Fixes and changes in 4.2BSD, section 39
csh In the third line, add the word, 'be', after the word,
'to.'
script
Last phrase should probably be 'at a terminal.'
sdb We are told that "it still lives on in/usr/src/old for
those with a personal attachment." However, if anyone
does have such an attachment, they are doomed to
unrequited love since /usr/src is a private directory.
stty The defaults mentioned here disagree with those given
on the manual page.
su Changes noted do not appear on manual page. I could
not get the extra argument business to work:
su myfriend 'ls /u/gsis/myfriend'
evoked:
ls /u/gsis/myfriend: File or directory not found
tail Need something after the word, 'similar.'
J. K. Cohen
4.2BSD -3-
An Introduction to the C Shell, section 40
p2. The mail example shows a visible EOT signal being sent
to the terminal, and the text claims the characters,
'EOT', are echoed by the mail program. However, these
characters do not really appear at the terminal.
It is stated that the uparrow character will be used to
represent the control key. This conflicts with other
documents in this volume and conflicts with internal
usage in this document. For on pages 14-16, we find
uparrow being used in the discussion of history to
represent the hat character.
Locally, you get reasonable terminal characteristics
without using 'tset'. In particular, the default is
that the backspace key works fine.
p3. The command 'ls -s' gives file sizes in terms of
kilobytes (1024 characters) instead of in terms of
blocks of 512 characters.
p4. Again, 'ls -s' is said to use 512 character blocks
instead of the actual 1024.
p7. The first complete sentence on this page ('There exists
...'), is confusing because the list at the end of this
lengthy beast uses ',' instead of 'or' as the delimiter
between cases. Making a list of cases would be yet a
better solution.
The local interrupt signal is 'break' (control-c) not
'del.'
p8. The example may mislead the novice into believing that
people can put files into his/her directories. Rest
easy, dear novice, your directories are default
protected against such intrusions both on this system
and on any professionally administered UNIX system.
Except for the system administrator (aka 'super user',
aka 'support'), no one can write in any of your
directories unless you take special action (see the
'chmod' command) to allow them to do so. Again a
visible EOT is shown.
p9. Again, a claim is made for the appearance of a visible
EOT.
Third sentence of second paragraph gives the shell
human attributes (it can be 'provoked', but apparently
only sometimes).
J. K. Cohen
4.2BSD -4-
After the example of using the command, 'more', as a
filter, we find the awkward phrase, 'more simple more'.
p11. The example of a typical .login could be made more
useful if here, or elsewhere, a more complete
explanation was given.
The method shown of setting the terminal
characteristics is archaic (e.g. the option -s is no
longer even documented in TSET(1)).
The 'msgs' command does not currently function here.
The if-then-endif structure shown at the end of the
.login fails if one (see CSH(1), page 16) puts:
set mail=(300 /usr/spool/mail/username)
or the like.
It is stated that the default 'mail check' interval is
5 minutes; it seems to be 10 minutes as stated in
CSH(1), page 16.
p14-15.
The commands 'num' and 'ssp' do not exist.
p14-16.
As noted above, uparrow (defined as control key) is
used when the hat character is meant.
p15. To make the alias examples intelligible, it should be
explained that !* is the history notation for all
arguments of the previous (i.e. unaliased) command and
similarly that !^ means the first argument (and while
we are at it that !$ means the last argument).
p17. In the first sentence of the last paragraph, the word
'background' is misspelled.
p19. Before first example, 'background' is misspelled again.
Why does the 'ls' command produce only one process
number (cf. same command and explanation thereof on
page 18)?
p23. This is scary, but despite the explicit note about the
\ inside the quotes, I found that I got exactly the
prompt whether or not I used the \. (cf. my comments
about the same issue under 'csh' in part I of this
Critique).
J. K. Cohen
4.2BSD -5-
The reference to the repeat command (which has limited
usefulness since it iterates only a simple command)
might well be supplemented with a scaled down (and
improved!) version of the following shell program:
#! /bin/csh
# Usage: loop ntimes cmd ...
# Repeat group of commands n times
# Note: The built-in, 'repeat' works only on simple cmds.
# Note: Quote cmds with args, eg., loop 2 "sleep 10" who
set c=$0
set c=$c:t
set N=$#argv
if ($N < 2) then
echo Usage $c ntimes cmd ...
exit(1)
endif
@ x = $1
shift
@ N--
while ($x)
@ i = 1
while ($i <= $N)
$argv[$i]
@ i++
end
@ x--
end
The discussion of setenv needs to be supplemented with
some discussion of what an 'environment' is.
p25ff.
There should be far more examples of shell programs to
illustrate the many items mentioned all too fleetingly
in this part of the tutorial.
p25. In 4.2BSD, it would be better to start csh files with
#! /bin/csh
instead of just an arbitrary comment line. In fact, if
the first line of the file is
#! /bin/sh
then despite the fact that the file begins with a #
line, it will be handled by the Bourne shell
interpreter.
J. K. Cohen
4.2BSD -6-
p26. Near the bottom of the page the wrong form of 'echo' is
cited, it should be:
echo -n 'yes or no? '
p27. At midpage the 'd' is omitted from 'replaced.'
p29. I had trouble using set n=$0:t in shell scripts. (so
the program would be able to 'know' its name for error
messages). I found that set n=$0, followed by set
n=$n:t worked, but I have no idea why!
p30. I advocate illustrating the structures shown; this is
supposed to be a tutorial.
p31. A comment should be added, explaining what the
'oldstring' is in the ed 's' command. Note that here
the uparrow is again used in the non- control key
sense.
Section 3.10 is too terse to be of any use. And then
one-third of it re-explains the archaic usage of # to
distinguish Bourne from C shells.
p37. In the last paragraph, 'messages' is misspelled.
J. K. Cohen
--
Jack Cohen
{nbires|denelcor|hao}!udenva!jkcohen