pwolfe@kailand.kai.com (Patrick Wolfe) (12/13/89)
I'm not complaining, just making a note of something that surprised me, and
which may affect other people.
I've found something that acts different in Bash than in Csh (the shell I
previously used). To place a multiple command list in the background, it is
neccessary to use parens to enclose the command. For example:
date ; make ; date &
with Bourne Shell or Bash 1.04, runs the first two commands in the foreground
and the last in the background, where C shell will create a background job
which runs all three commands. To do the same thing with sh or bash (and
probably ksh too), you must enclose the command list within parens:
( date ; make ; date ) &
Whoever is writing the documentation might want to mention this as a conversion
aid for folks (like me) who are used to the way C shell works.
--
Patrick Wolfe (pwolfe@kai.com, ...!kailand!pwolfe)
System Manager, Kuck & Associatesnews@bbn.COM (News system owner ID) (12/22/89)
pwolfe@kailand.kai.com (Patrick Wolfe) writes:
< I've found something that acts different in Bash than in Csh (the shell I
< previously used). To place a multiple command list in the background, it is
< neccessary to use parens to enclose the command. For example:
<
< date ; make ; date &
<
< with Bourne Shell or Bash 1.04, runs the first two commands in the foreground
< and the last in the background, where C shell will create a background job
< which runs all three commands.
I'll have to re-read the csh man page, but at a glance I *swear* this
is a csh misfeature (aka. deliberate bug). The csh man page is vague.
From csh(1):
Pipelines can be separated by semicolons (;), in which case
they are executed sequentially. Pipelines that are separated
by && or || form conditional sequences in which the execu-
tion of pipelines on the right depends upon the success or
failure, respectively, of the pipeline on the left.
[The way I read the above, "foo && bar" is a (conditional) sequence,
but "foo; bar" may or may not be an unconditional sequence.]
A pipeline or sequence can be enclosed within parentheses `(
)' to form a simple command that can be a component in a
pipeline or sequence.
A sequence of pipelines can be executed asynchronously, or
in the background by appending an `&'; rather than waiting
for the sequence to finish before issuing a prompt, the
shell displays the job number (see Job Control, below) and
associated process IDs, and prompts immediately.
Anyway, in every other shell I've ever heard of ; and & are at the
same precedence level. It's easier to remember, and more intuitive.
Please let's keep bash the way it is, and force people to do
(foo; bar) &
like they should have been doing in the first place.
-- Paul Placewaytrost@reed.bitnet (Bill Trost) (12/27/89)
[Various people writing things about & in csh, including...] Article <50009@bbn.COM>, by pplacewa@antares.bbn.com (Paul W Placeway): >I'll have to re-read the csh man page, but at a glance I *swear* this >is a csh misfeature (aka. deliberate bug). The csh man page is vague. >From csh(1): .... Though I can't find the reference at the moment, it seems as though something stated that ';' had a higher precedence than '&' in the csh. Sorry to belabor this in this mailing list --- the csh does it wrong, in any case.