#9952: make SAGE_CHECK work with SAGE_ATLAS_LIB
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Reporter: jhpalmieri | Owner: tbd
Type: defect | Status: needs_review
Priority: minor | Milestone: sage-4.6
Component: packages | Keywords:
Author: John Palmieri | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by drkirkby):
Replying to [comment:3 leif]:
> Hmmm, the latter is much nicer (and works with all shells / {{{test}}}
programs).
>
> Some dead old are only broken in comparing empty strings with {{{=}}} or
{{{!=}}}; {{{-z}}} and {{{-n}}} always work (otherwise wouldn't make sense
at all).
Actually, I'd have to disagree with that. I've been using -z and -n, as I
agree it looks cleaner, but this is a quote from the autoconf mailing
list:
http://lists.gnu.org/archive/html/autoconf/2010-09/msg00030.html
says
''this is yet another case of @var{string} that looks like an operator,
and yet another reason that you should ALWAYS use test x"$val" = x rather
than test -z "$val" if you don't know what $val contains.''
The autoconf developers have a '''huge''' experience in writing code as
portable as possible, so I'm going to switch to the the more portable
{{{"x$var" = x}}}. IMHO, for questions of portability, the autoconf
mailing list is the best place to ask.
You can argue rightly argue it does not matter with bash, which this shell
is, but it does matter with some shells. So I would '''personally'''
choose to use the most portable way, so things I write do not rely on
bash, but would work with just about any shell. But it's a matter of
style. Let John choose what he wants. I believe in order of decreasing
portability, they are:
* {{{ if [ "x$var" = x ] ; then}}}
* {{{ if [ -z "$var" ] ; then}}}
* {{{ if [ "$var" = "" ] ; then}}}
But all work with modern bash shells. But my '''personal''' preference is
for the first of these, since it would appear to be the most portable.
Dave
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9952#comment:7>
Sage <http://www.sagemath.org>
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