* Anonymous array indexing @ 2000-12-13 1:41 Steve Talley 2000-12-13 4:04 ` Dan Nelson 2000-12-13 4:06 ` Bart Schaefer 0 siblings, 2 replies; 5+ messages in thread From: Steve Talley @ 2000-12-13 1:41 UTC (permalink / raw) To: zsh-users Hello, Is there a compact version of the following: fred=(one two three) export FRED=$fred[2] unset fred I am looking for something like export FRED=(one two three)[2] so that I can avoid having to use the temporary variable fred. The above doesn't work. Is there something equivalently short I can use? I'm running zsh 3.1.9. Thanks, Steve ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Anonymous array indexing 2000-12-13 1:41 Anonymous array indexing Steve Talley @ 2000-12-13 4:04 ` Dan Nelson 2000-12-13 4:06 ` Bart Schaefer 1 sibling, 0 replies; 5+ messages in thread From: Dan Nelson @ 2000-12-13 4:04 UTC (permalink / raw) To: Steve Talley; +Cc: zsh-users In the last episode (Dec 12), Steve Talley said: > Is there a compact version of the following: > > fred=(one two three) > export FRED=$fred[2] > unset fred > > I am looking for something like > > export FRED=(one two three)[2] Assuming "one two three" is actually stored in a shell variable (we'll call it a): export FRED=${${=a}[2]} will work. = turns on SH_WORD_SPLIT, essentially turning the variable into an array temporarily. -- Dan Nelson dnelson@emsphone.com ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Anonymous array indexing 2000-12-13 1:41 Anonymous array indexing Steve Talley 2000-12-13 4:04 ` Dan Nelson @ 2000-12-13 4:06 ` Bart Schaefer 2000-12-13 17:05 ` Steve Talley 1 sibling, 1 reply; 5+ messages in thread From: Bart Schaefer @ 2000-12-13 4:06 UTC (permalink / raw) To: zsh-users On Dec 12, 6:41pm, Steve Talley wrote: } } Is there a compact version of the following: } } fred=(one two three) } export FRED=$fred[2] } unset fred } } so that I can avoid having to use the temporary variable fred. The general trick is that the nameless parameter ${} always expands to the empty string, so ${:-value} always expands to "value". Then build up from there. } I am looking for something like } } export FRED=(one two three)[2] The value in ${:-value} always starts out as a scalar (a string), so you have to explicitly convert to an array before you can index it. If the individual words of the array do not contain spaces, you can combine word splitting ${=scalar} with ${:-value} to get: export FRED=${${=:-one two three}[2]} If the words will have embedded spaces, you'll have to resort to some other kind of splitting. E.g., ${(f)...} splits at newlines, so you can do: export FRED=${${(f):-$'one\ntwo has spaces\nthree'}[2]} This uses $'...' to turn \n into newlines, then splits on them. However, the $'...' syntax is not available in 3.0.x. In all versions you can instead split on some other character, e.g. on period: export FRED=${${(s(.)):-one.two has spaces.three}[2]} I don't think there is a fully general solution that works when you can't choose in advance a character on which to split. However, I'm guessing that the strings in the array are known in advance, and that it is the subscript that might vary, so you should be able to work something out. -- Bart Schaefer Brass Lantern Enterprises http://www.well.com/user/barts http://www.brasslantern.com Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Anonymous array indexing 2000-12-13 4:06 ` Bart Schaefer @ 2000-12-13 17:05 ` Steve Talley 2000-12-13 17:39 ` Bart Schaefer 0 siblings, 1 reply; 5+ messages in thread From: Steve Talley @ 2000-12-13 17:05 UTC (permalink / raw) To: Bart Schaefer; +Cc: zsh-users Thanks Bart/Dan for the replies! This _almost_ solves my problem, although I think I oversimplified. The actual usage of this is in: # Find a value for TERMINFO by looking for xterm package delegates=(5.9 5.8.1 5.8 5.7 5.6) terminfo=( $HOME/$^delegates/pkgs/xterm/lib/terminfo(/) ) export TERMINFO=$terminfo[1] unset terminfo Unfortunately this doesn't work well with your solution, ie. export TERMINFO=${${=:-$HOME/$^delegates/pkgs/xterm/lib/terminfo(/)}[2]} doesn't even come close to working. Any ideas for this slightly more complicated example? Thanks, Steve Bart Schaefer wrote: > On Dec 12, 6:41pm, Steve Talley wrote: > } > } Is there a compact version of the following: > } > } fred=(one two three) > } export FRED=$fred[2] > } unset fred > } > } so that I can avoid having to use the temporary variable fred. > > The general trick is that the nameless parameter ${} always expands to the > empty string, so ${:-value} always expands to "value". Then build up from > there. > > } I am looking for something like > } > } export FRED=(one two three)[2] > > The value in ${:-value} always starts out as a scalar (a string), so you > have to explicitly convert to an array before you can index it. > > If the individual words of the array do not contain spaces, you can combine > word splitting ${=scalar} with ${:-value} to get: > > export FRED=${${=:-one two three}[2]} > > If the words will have embedded spaces, you'll have to resort to some other > kind of splitting. E.g., ${(f)...} splits at newlines, so you can do: > > export FRED=${${(f):-$'one\ntwo has spaces\nthree'}[2]} > > This uses $'...' to turn \n into newlines, then splits on them. However, > the $'...' syntax is not available in 3.0.x. In all versions you can > instead split on some other character, e.g. on period: > > export FRED=${${(s(.)):-one.two has spaces.three}[2]} > > I don't think there is a fully general solution that works when you can't > choose in advance a character on which to split. However, I'm guessing > that the strings in the array are known in advance, and that it is the > subscript that might vary, so you should be able to work something out. > > -- > Bart Schaefer Brass Lantern Enterprises > http://www.well.com/user/barts http://www.brasslantern.com > > Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Anonymous array indexing 2000-12-13 17:05 ` Steve Talley @ 2000-12-13 17:39 ` Bart Schaefer 0 siblings, 0 replies; 5+ messages in thread From: Bart Schaefer @ 2000-12-13 17:39 UTC (permalink / raw) To: Steve Talley; +Cc: zsh-users On Dec 13, 10:05am, Steve Talley wrote: } Subject: Re: Anonymous array indexing } } # Find a value for TERMINFO by looking for xterm package } delegates=(5.9 5.8.1 5.8 5.7 5.6) } terminfo=( $HOME/$^delegates/pkgs/xterm/lib/terminfo(/) ) } export TERMINFO=$terminfo[1] } unset terminfo } } Unfortunately this doesn't work well with your solution, ie. } } export TERMINFO=${${=:-$HOME/$^delegates/pkgs/xterm/lib/terminfo(/)}[2]} You've got two problems. One is that you're trying a file glob, which isn't going to work in the same shell-word with TERMINFO= (unless you resort to using `setopt globassign'). Two is that =:- is in the wrong place. For the second problem, you'd want $HOME/${^${=:-5.9 5.8.1 5.8 5.7 5.6}}/pkgs/xterm/lib/terminfo(/) You can get around the glob problem by using $(print ...), but I don't know why avoiding a temp parameter would be important enough to fork a new process. export TERMINFO=${$(print \ $HOME/${^${=:-5.9 5.8.1 5.8 5.7 5.6}}/pkgs/xterm/lib/terminfo(/))[1]} -- Bart Schaefer Brass Lantern Enterprises http://www.well.com/user/barts http://www.brasslantern.com Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2000-12-13 17:39 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2000-12-13 1:41 Anonymous array indexing Steve Talley 2000-12-13 4:04 ` Dan Nelson 2000-12-13 4:06 ` Bart Schaefer 2000-12-13 17:05 ` Steve Talley 2000-12-13 17:39 ` Bart Schaefer
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