3.9. Gotchas in set prompt Test
Lots of users add an if (! $?prompt)
exit test to their .cshrc
files. It's gotten so common that some vendors add a
workaround to defeat the test. For instance, some versions of the
command (Section 2.6) set the prompt variable
so that it can see your aliases
"hidden" inside the
$?prompt test. I've also seen a
version of at that starts an interactive shell to
If you've buried commands after
if (! $?prompt) that should
only be run on interactive shells or at login time, then you may have
There are workarounds. What you'll need depends on
the problem you're trying to work around.
The version of which on the CD-ROM [see http://examples.oreilly.com/upt3] works without
reading your .cshrc file, so
there's no problem there.
Here's a way to stop the standard
which from reading parts of your
.cshrc that you don't want it
to read. The first time you log in, this scheme sets a
environment variable (Section 35.3). The variable will be copied into all
(Section 24.4) (like the one that which
starts). In subshells, the test if
($?CSHRC_READ) will branch to the end of your
if (! $?prompt) goto cshrc_end
# COMMANDS BELOW HERE ARE READ ONLY BY INTERACTIVE SHELLS:
alias foo bar
if ($?CSHRC_READ) goto cshrc_end
# COMMANDS BELOW HERE ARE READ ONLY AT LOGIN TIME:
setenv CSHRC_READ yes
If you have a buggy version of at
(Section 25.5) that runs jobs from interactive
shells, make your own frontend to
at (Section 29.1)
that sets an
environment variable named AT temporarily before
it submits the at job. Add a test to your
.cshrc that quits if AT is
( ) Section 43.7, \at Section 29.8
# at JOBS RUN INTERACTIVE SHELLS ON MY BUGGY VERSION OF UNIX.
# WORKAROUND IS HERE AND IN THE at ALIAS BELOW:
if ($?AT) goto cshrc_end
alias at '(setenv AT yes; \at \!*)'
Most modern versions of at save a copy of your
environment when you submit the job and use it when the
at job is run. At that time, the
AT environment variable will be set; the C shell
will skip the parts of your .cshrc that you want
it to. It's ugly, but it works.
Those workarounds probably won't solve all the
problems on your version of Unix, but I hope they'll
give you some ideas.
--JP and SJC
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