2015-02-20 18:13 GMT-02:00 David Korn <dgk...@gmail.com>:
> Yes, this is intentional. By default, pathname expansion applies to all
> arguments to simple commands. You can do set -o noglob to turn off pathname
> expansion. You can do IFS='' to disable command splitting.
>
> It can also be useful with typeset, for example
> typeset -a files=(*)
Thanks. I believe this may be a bit confusing at first,
because sometimes it will expand the variable name,
and sometimes will error. The use of '*' and '?' are just
to show the glob expansion, but use of '[' and ']' may
be confusing.
The original problem report I have is due to shell
like this:
---8<---
$ cat test.sh
#!/bin/ksh93
typeset -A stuff
typeset -lui i=0
for (( i=0; i<100000; i++ ))
do
unset stuff[xyz]
done
---8<---
and this:
---8<---
$ /usr/bin/strace -e trace=getdents ./test.ksh 2>&1 | /bin/grep -c getdents
200000
---8<---
The way to fix this is to quote, as in unset 'stuff[xyz]',
but this may look wrong for some people, so I did
want to have some insight if it is expected or not.
> On Fri, Feb 20, 2015 at 9:13 AM, Clark Wang <dearv...@gmail.com> wrote:
>>
>> On Thu, Feb 19, 2015 at 2:48 AM, Paulo César Pereira de Andrade
>> <paulo.cesar.pereira.de.andr...@gmail.com> wrote:
>>>
>>> Consider these sequences:
>>
>>
>> The results are all expected and the pathname expansion has nothing to do
>> with typeset.
>>>
>>>
>>> $ touch stuff
>>> $ typeset -A st*f
>>
>>
>> st*f would be expanded to stuff so this command is the same as typeset -A
>> stuff.
>>
>>>
>>> $ typeset | grep st
>>> associative array stuff
>>>
>>> $ set -o noglob
>>> $ typeset -A st*f
>>> ksh: typeset: st*f: invalid variable name
>>
>>
>> With -o noglob, st*f would not expand so this command is the same as
>> typeset -A "st*f". And as the error message indicated it's not a valid var
>> name.
>>>
>>>
>>> $ set -o glob
>>> $ touch stuff[xyz]
>>
>>
>> This creates a file named "stuff[xyz]".
>>
>>>
>>> $ typeset -A st*f[xyz]
>>> ksh: typeset: st*f[xyz]: invalid variable name
>>
>>
>> Since no files match the pattern, st*f[xyz] would "expand" to itself so
>> this command is the same as typeset -A "st*f[xyz]" and again it's not a
>> valid var name.
>>
>>>
>>> typeset -A st*f\[xyz\]
>>
>>
>> st*f\[xyz\] expands to the filename stuff[xyz] so this command is the same
>> as typeset -A "stuff[xyz]" which declares stuff[xyz] as an associative
>> array.
>>
>>>
>>> $ typeset -A stuff[x*z]
>>
>>
>> No files match stuff[x*z] so it expands to stuff[x*z] so this command is
>> the same as typeset -A "stuff[x*z]" which declares stuff["x*z"] as an
>> associative array.
>>
>>>
>>> $ typeset -A stuff[x?z]
>>
>>
>> Ditto.
>>
>>>
>>> $ typeset -A stuff\[x*z\]
>>
>>
>> The pattern expands to the filename "stuff[xyz]" so this command is the
>> same as typeset -A "stuff[xyz]" which declares stuff[xyz] as an associative
>> array.
>>
>>>
>>> $ typeset -p | grep stuff
>>> typeset -A stuff=(['x*z']=() ['x?z']=() [xyz]=() )
>>
>>
>> So this result is as expected.
>>
>> -clark
>>>
>>>
>>> I believe this may not have been intended, as other ways
>>> to create shell variables do not do path expansion.
Thanks,
Paulo
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