[Cialug] Bash looping issue

[Crouse]

ah nm... that went horribly wrong ;)


On Wed, Oct 13, 2010 at 1:12 PM, Crouse <crouse at usalug.net> wrote:
> On Wed, Oct 13, 2010 at 11:18 AM, Ken MacLeod <ken at bitsko.slc.ut.us> wrote:
>> On Tue, Oct 12, 2010 at 10:07 AM, Daniel A. Ramaley
>> <daniel.ramaley at drake.edu> wrote:
>>> In the example script below, i define an associative array and then make
>>> a copy of it using a loop to copy each key/value pair. It seems to work
>>> quite nicely... within the loop. Once outside the loop, the copied array
>>> loses its data. The bizarre thing is that if i switch the loop construct
>>> from a "while" to a "for", it works.
>>
>>> # Comment out the "printf...while" loop and comment in the "for" loop
>>> # and it magically starts working. I don't know why.
>>> printf "%s\000" "${!ORIG[@]}" | sort -z | while read -d $'\0' key ; do
>>> #for key in "${!ORIG[@]}" ; do
>>
>> My first thought is that the "while" is running in a pipeline so it's
>> running in a subprocess rather than the current process, so any
>> variables inside the loop are local to the subprocess.  However, I
>> thought I've done that before too and it worked right...
>>
>> You might try:
>>
>>    while read -d $'\0' key <(printf "%s\000" "${!ORIG[@]}" | sort -z); do
>>
>> so the printf | sort runs in a background process and the while stays
>> in the current process.  I've never tried that before but it popped up
>> when I went looking for the other kinds of "fancy" pipe handling that
>> I know bash has ;-)
>>
>>  -- Ken
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>>
>
> If your just copying an array, do you need to use the while loop ?
>
> #!/bin/bash
> declare -A ORIG
> ORIG=(['key 1']='A'
>     ['key 2']='B'
>     ['key 3']='C')
>
> COPY=("${ORIG[@]}")
>
> echo -e "\nORIG\n----"
> for key in "${!ORIG[@]}" ; do     # Prints the ORIG array.
>   echo -e "$key\t${ORIG[$key]}"
> done
>
> echo -e "\nCOPY\n----"
> for key in "${!COPY[@]}" ; do     # Prints COPY only if it was created
>   echo -e "$key\t${COPY[$key]}" # with "for" loop--prints nothing if
> done                              # created with "while".
>