[GRASS-dev] gis.m in wingrass: using where clause in d.vect causes error :can't read "_data(.gronsole.gronsole, 9, donecmd)": no such element in array

[Moritz Lennert]

On Tue, October 10, 2006 05:22, Glynn Clements wrote:
>
> Moritz Lennert wrote:
>
>> >> Huidae or Glynn, any ideas on this ?
>> >
>> > 	# Actually run the program
>> > 	if { $mingw == "1" } {
>> > 		# shell scripts require sh.exe.
>> > 		set cmd [concat | sh -c '$cmd']
>> > 	} else {
>> > 		set cmd [concat | $cmd 2>@ stdout]
>> > 	}
>> >
>> > If you want to use "sh -c ...", you have to escape any shell
>> > metacharacters, otherwise commands which happen to contain shell
>> > metacharacters (e.g. "<" or ">" in a SQL "WHERE" clause) won't work.
>> >
>> > I've already explained this in the thread discussing these changes.
>>
>> Found
>> http://grass.itc.it/pipermail/grass5/2006-September/025834.html
>>
>> where you say
>>
>>  "The simplest solution to the issue of
>>  metacharacters is to replace any occurrences of the single quote
>>  character in arguments with "'\''" (quote, backslash, quote, quote)
>>  and surround each argument with single quotes.
>>
>>  Even then, there might be issues due to the shell messing with the
>>  environment, signal handling, process groups etc (as well as possible
>>  Unix-compatibility "features"). Shells are very complex programs."
>>
>> Not sure that I understand exactly what needs to be done and where.
>
> In the above Tcl code, $cmd is a Tcl list (a string using a specific
> syntax which ensures that element boundaries are preserved even when
> elements contain spaces etc).
>
> Using that string as an argument to "sh -c ..." will only work
> correctly if the format of the string is such that the shell will
> parse it into the same list of strings that Tcl would. In practice,
> this will only happen if none of the elements contain any characters
> which are significant to either Tcl or the shell (which includes
> spaces, as they are normally treated as element separators).
>
> IOW, "sh -c '$cmd'" will only work for commands where none of the
> arguments contain either Tcl or shell metacharacters. If you want to
> invoke $cmd via "sh -c ...", you have to take the list apart and
> construct a command line using shell syntax.
>
> E.g. (untested):
>
> 	set shcmd ""
> 	foreach arg $cmd {
> 		set arg2 [regsub -all {'} $arg {'\''}]
> 		if {$shcmd == ""} {
> 			set shcmd "'$arg2'"
> 		} else {
> 			set shcmd "$shcmd '$arg2'"
> 		}
> 	}
> 	set cmd [concat | sh -c $shcmd]

Finally gotten around to trying this. After adding simple quotes to the
last line:

      set cmd [concat | sh -c '$shcmd']

I don't get the error anymore, but it still doesn't work as it should:

comcod=21004 works

but comcod=21004 and comcod=21005

only show comcod=21004, not 21005

and comcod>21004 doesn't show anything, but doesn't produce an error message.


>
> However, for various reasons, it would be better if we could find a
> way avoid using "sh -c ..." altogether. The problem there is that you
> can't directly execute shell scripts on Windows.

agreed, but have we found a way for doing this, yet, at least theoretically ?

Moritz