From: norman@oclsc.org (Norman Wilson)
Subject: [TUHS] Shell control through external commands
Date: Mon, 12 Sep 2016 08:56:56 -0400 [thread overview]
Message-ID: <1473685021.9119.for-standards-violators@oclsc.org> (raw)
Joerg Schilling:
The colon was introduced by AT&T around 1983. It was used for Bourne Shell
scripts. Some of these scripts made it into SVr4 and caused problems with
non-Bourne compatible other shells.
====
Interesting. I never knew of that convention. I remember seeing
shell scripts with a : at the front, but thought that was just to
make sure the first character wasn't # even if the script began with
a comment.
Since some here had never heard of the #-means-csh convention, I
should perhaps explain about :. In pre-Bourne shells that used the
simple external control-flow mechanisms that I think were discussed
here a few months ago, : was used to mark a label: goto(1) would
seek to the beginning of its standard input, then read until it
encountered a line of the form
: label
with the desired label, then exit with the seek pointer at the first
character of the following line.
: was a no-op command; I forget whether it was implemented within the
shell or externally. Either way, that made it useful as a comment
character, but somewhat clumsy: it was just a command, with no
special parsing rules attached. A comment using : had to begin at
a command boundary, and its arguments were parsed in the normal way:
rm -rf * : you don't want to do this
was probably not what you wanted, instead you had to type
rm -rf * ; : "you don't want to do this"
or the like.
csh used # as a comment character from the beginning. Bourne
adopted it too.
Norman Wilson
Toronto ON
next reply other threads:[~2016-09-12 12:56 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-12 12:56 Norman Wilson [this message]
-- strict thread matches above, loose matches on Subject: below --
2016-09-12 12:57 Norman Wilson
2016-09-12 1:43 Norman Wilson
2016-09-12 9:18 ` Joerg Schilling
2016-09-12 1:31 Norman Wilson
2016-09-12 9:33 ` Joerg Schilling
2016-09-12 0:27 Doug McIlroy
2016-09-11 17:39 Doug McIlroy
2016-09-11 18:11 ` Clem Cole
2016-09-11 18:27 ` Dan Cross
2016-09-11 18:50 ` Sven Mascheck
2016-09-11 22:13 ` Random832
2016-09-10 14:57 Nemo
2016-07-15 16:47 Doug McIlroy
2016-09-10 17:40 ` Dario Niedermann
2016-09-10 19:22 ` arnold
2016-09-12 8:35 ` markus schnalke
2016-09-12 9:25 ` Joerg Schilling
2016-09-12 12:41 ` Tony Finch
2016-09-12 12:50 ` Joerg Schilling
2016-09-13 0:17 ` Sven Mascheck
2016-09-13 1:45 ` Sven Mascheck
2016-09-13 9:20 ` Joerg Schilling
2016-09-12 20:12 ` Dave Horsfall
2016-09-12 21:36 ` Dave Horsfall
2016-09-10 22:43 ` Dave Horsfall
2016-09-11 1:24 ` Ron Natalie
2016-09-11 2:39 ` arnold
2016-09-11 2:41 ` Ronald Natalie
2016-09-11 4:07 ` Dave Horsfall
2016-09-11 5:01 ` arnold
2016-09-12 5:49 ` Dave Horsfall
2016-07-15 12:27 Norman Wilson
2016-09-10 7:45 ` Dario Niedermann
2016-09-10 9:13 ` Michael Kjörling
2016-09-10 9:41 ` Joerg Schilling
2016-09-10 17:06 ` Random832
2016-09-10 17:45 ` Dario Niedermann
2016-09-10 19:53 ` Dan Cross
2016-09-10 20:02 ` Chet Ramey
2016-09-10 20:27 ` Dario Niedermann
2016-09-11 10:03 ` Diomidis Spinellis
2016-09-12 10:05 ` Jacob Goense
2016-07-15 4:29 Rudi Blom
2016-07-14 13:18 Diomidis Spinellis
2016-07-14 13:23 ` Clem Cole
2016-07-14 14:12 ` Mary Ann Horton
2016-07-14 22:36 ` Dave Horsfall
2016-07-14 22:47 ` Corey Lindsly
2016-07-14 22:49 ` Peter Jeremy
2016-07-14 23:27 ` Marc Rochkind
2016-07-15 10:13 ` Joerg Schilling
[not found] ` <CAH_OBieVFzPn93L8=_fmbUycZ7UmYdXiopC0vgei6RGDZp0mHw@mail.gmail.com>
[not found] ` <CAH_OBie_6gFy+BqkCMj+sr0NqTMNOQxvgWf6SQnHMJpn7DAytA@mail.gmail.com>
2016-07-14 23:56 ` shawn wilson
2016-07-15 1:04 ` Dave Horsfall
2016-07-15 1:22 ` Steve Nickolas
2016-07-15 2:25 ` arnold
2016-07-16 6:26 ` Dave Horsfall
2016-07-15 2:25 ` Random832
2016-07-15 3:59 ` Dave Horsfall
2016-07-15 4:09 ` Random832
2016-07-15 13:55 ` Chet Ramey
2016-07-14 23:10 ` Ronald Natalie
2016-07-15 1:41 ` Nemo
2016-07-15 9:00 ` Tony Finch
2016-07-14 14:11 ` schoedel
2016-07-14 14:38 ` Diomidis Spinellis
2016-07-14 15:46 ` John Cowan
2016-07-14 16:30 ` Random832
2016-07-14 22:32 ` Dave Horsfall
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