[Cialug] Bash looping issue

[Crouse]

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".