From: culliton@srg.af.mil (Tom Culliton x2278)
To: rc@hawkwind.utcs.toronto.edu
Subject: Command execution
Date: Wed, 24 Jun 1992 15:10:38 -0400 [thread overview]
Message-ID: <9206241510.aa06947@ceres.srg.af.mil> (raw)
Heres a minor annoyance/inconsistency with Byron's rc that I noticed
way back when I first started using it but never bugged me until now.
Tom Duff[1] says that in executing commands rc first looks for a
function of the given name, then a builtin commands, then if the name
CONTAINS a '/' it is taken as a path to an executeable, otherwise it
searchs for an executable of that name using the path.
This implies a couple of things which I believe are desirable. First,
the function: "fn csh /bin/csh { echo 'You''ve got to be kidding!' }"
should be a legitimate and useful definition. If you really want to
get to csh you can still say "builtin csh". (Unless of course builtin
has been overloaded...) Currently "/bin/csh" will not invoke the
function.
Second, the commands "./bin/thingee" and "bin/thingee" should be
treated consistently, and not behave differently, based on the path or
function definitions. Currently if you remove "." from your path
"bin/thingee" will not be treated as a path name, and "bin/thingee"
will invoke a function but "./bin/thingee" will not.)
Unfortunately Byron[2] changed these rules somewhat, so that his rc
FIRST checks if the command STARTS with "/", "./", or "../" in which
case it is taken as a path to an executeable, before going on to check
functions, builtins and the path. This means that the function
"/bin/csh" will never be seen and that "./bin/thingee" is quite
different from "bin/thingee".
"Fixing" this should be trivial, in the one case changing the order of
checks and in the other checking using strchr(cmdname, '/'). However I
assume Byron had a reason for this. Any comments?
Tom
[1] "Rc - A Shell for Plan 9 and Unix Systems", page 6, section 17
[2] "RC(1)" (Byron's man page), page 1, section "Commands"
next reply other threads:[~1992-06-24 19:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
1992-06-24 19:10 Tom Culliton x2278 [this message]
1992-06-24 20:19 ` Chris Siebenmann
1992-06-24 21:19 Tom Culliton x2278
1992-06-24 23:04 ` David Moore
1992-06-25 21:22 ` Chris Siebenmann
1992-06-25 21:56 Tom Culliton x2278
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9206241510.aa06947@ceres.srg.af.mil \
--to=culliton@srg.af.mil \
--cc=rc@hawkwind.utcs.toronto.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).