RE: [PATCHv2] completion: make compatible with zsh
- From
Peter Kjellerstedt <peter.kjellerstedt@axis.com>
- Date
- Aug 31, 2010, 07:52 UTC
- Message-ID
- <A612847CFE53224C91B23E3A5B48BAC749BF0BEBB9@xmail3.se.axis.com>
- In-Reply-To
- <AANLkTimNULQNVZ4hzaNY1ZobPRtj_zj545Xi29guGu4g@mail.gmail.com>
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> -----Original Message----- > From: git-owner@vger.kernel.org [mailto:git-owner@vger.kernel.org] On > Behalf Of Mark Lodato > Sent: den 31 augusti 2010 02:56 > To: SZEDER Gábor > Cc: Shawn O. Pearce; git@vger.kernel.org; avarab@gmail.com; Jonathan > Nieder; Andrew Sayers > Subject: Re: [PATCHv2] completion: make compatible with zsh > > 2010/8/30 SZEDER Gábor <szeder@ira.uka.de> > > On Thu, Aug 26, 2010 at 10:45:56PM -0400, Mark Lodato wrote: > > > @@ -2417,3 +2433,29 @@ if [ Cygwin = "$(uname -o 2>/dev/null)" ]; then > > > complete -o bashdefault -o default -o nospace -F _git git.exe 2>/dev/null \ > > > || complete -o default -o nospace -F _git git.exe > > > fi > > > + > > > +if [[ -z $ZSH_VERSION ]]; then > > > > -z? I think you wanted to use -n here, like at the other places. > > Oh, yes, sorry. This was a mistake. Thanks for catching it. > > > > Nit: why "if [[ ... ]]"? FWIW "if [ ... ]" would be enough. > > Because you don't need to quote variables with [[ ... ]] --- e.g. [ > $lines = 0 ] fails, though in this case this feature does not matter > --- and because [[ ... ]] is faster. > > Bash 4.1.5: > > time (for (( i = 0; i < 200000; i++ )); do [ -z $foo ]; done) > real 0m3.430s > user 0m3.240s > sys 0m0.180s > > time (for (( i = 0; i < 200000; i++ )); do [[ -z $foo ]]; done) > real 0m2.219s > user 0m2.090s > sys 0m0.100s > > Zsh 4.3.10: > > time (for (( i = 0; i < 2000000; i++ )); do [ -z $foo ]; done) > (; for ((i = 0; i < 2000000; i++ )) do; [ -z $foo ]; done; ) 13.56s > user 1.64s system 99% cpu 15.327 total > > time (for (( i = 0; i < 2000000; i++ )); do [[ -z $foo ]]; done) > (; for ((i = 0; i < 2000000; i++ )) do; [[ -z $foo ]]; done; ) 4.62s > user 0.01s system 99% cpu 4.644 total > > Is there a reason to prefer [ ... ] ?
The [ command is defined by POSIX, while [[ is an extension to the shell language implemented by bash (and zsh). Thus the [[ construct would fail on a stricter POSIX implementation of the shell language, e.g., as implemented by dash. Thus to be POSIX compliant (which is required for shell scripts installed by a multi system supporting application like git), the [[ construct cannot be used.
Of course, this does not really apply to a script explicitly written for bash, but that is the common reason to prefer [ over [[ in shell scripts.
//Peter