From: Peter Stephenson <Peter.Stephenson@csr.com>
To: <zsh-users@zsh.org>
Subject: Re: [[ and [
Date: Tue, 6 Mar 2012 16:29:16 +0000 [thread overview]
Message-ID: <20120306162916.50c71829@pwslap01u.europe.root.pri> (raw)
In-Reply-To: <4F563860.2040506@sergio.spb.ru>
On Tue, 6 Mar 2012 20:16:32 +0400
sergio <mailbox@sergio.spb.ru> wrote:
> than you for a good explanation. Hope you'll add it to the manual.
Actually, the description of test and [ already has this to say...
test [ arg ... ]
[ [ arg ... ] ]
Like the system version of test. Added for compatibility; use
conditional expressions instead (see the section `Conditional
Expressions'). The main differences between the conditional
expression syntax and the test and [ builtins are: these com‐
mands are not handled syntactically, so for example an empty
variable expansion may cause an argument to be omitted; syntax
errors cause status 2 to be returned instead of a shell error;
and arithmetic operators expect integer arguments rather than
arithmetic expressions.
The command attempts to implement POSIX and its extensions where
these are specified. Unfortunately there are intrinsic ambigui‐
ties in the syntax; in particular there is no distinction
between test operators and strings that resemble them. The
standard attempts to resolve these for small numbers of argu‐
ments (up to four); for five or more arguments compatibility
cannot be relied on. Users are urged wherever possible to use
the `[[' test syntax which does not have these ambiguities.
--
Peter Stephenson <pws@csr.com> Software Engineer
Tel: +44 (0)1223 692070 Cambridge Silicon Radio Limited
Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, UK
Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom
More information can be found at www.csr.com. Follow CSR on Twitter at http://twitter.com/CSR_PLC and read our blog at www.csr.com/blog
next prev parent reply other threads:[~2012-03-06 16:29 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-04 2:36 sergio
2012-03-04 4:24 ` Bart Schaefer
2012-03-06 0:32 ` sergio
2012-03-06 6:05 ` Bart Schaefer
2012-03-06 11:05 ` sergio
2012-03-06 11:35 ` Peter Stephenson
2012-03-06 11:44 ` Peter Stephenson
2012-03-06 11:53 ` Mikael Magnusson
2012-03-07 9:02 ` Nadav Har'El
2012-03-07 9:05 ` Mikael Magnusson
2012-03-07 9:21 ` Nadav Har'El
2012-03-07 15:27 ` Bart Schaefer
2012-03-07 8:52 ` Nadav Har'El
2012-03-07 9:43 ` Peter Stephenson
2012-03-07 14:11 ` Nadav Har'El
2012-03-07 14:27 ` Peter Stephenson
2012-03-07 18:38 ` Mark
2012-03-06 16:16 ` sergio
2012-03-06 16:29 ` Peter Stephenson [this message]
2012-03-06 17:40 ` sergio
2012-03-07 8:12 ` Nadav Har'El
2012-03-04 4:50 ` Kurtis Rader
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