How do you change a variable in a KSH if or case statement? - variables

Question

Does anyone know how to set a variable with global scope in a KSH if, case, or loop statement?
I am trying to run the following code but the script only echo's "H" instead of the actual value seen in the input file.
CFG_DIR=${WORK_DIR}/cfg
CFG_FILE=${CFG_DIR}/$1
NAME=$(echo $CFG_FILE | cut -f1 -d\.)
UPPER_BUS_NETWORK="H"
cat ${CFG_FILE} | grep -v ^\# |
while read CLINE
do
PROPERTY=$(echo $CLINE | cut -f1 -d\=)
VALUE=$(echo $CLINE | cut -f2 -d\=)
if [ ${PROPERTY} = "UpperBusService" ]; then
UPPER_BUS_SERVICE="${VALUE}"
fi
if [ ${PROPERTY} = "UpperBusNetwork" ]; then
UPPER_BUS_NETWORK="${VALUE}"
fi
done
echo ${UPPER_BUS_NETWORK}

Answer 1

Are you sure you're running that in ksh? Which version? Ksh93 doesn't set up a subshell in a while loop. Bash, dash, ash and pdksh do, though. I'm not sure about ksh88.
Compare
$ bash -c 'a=111; echo foo | while read bar; do echo $a; a=222; echo $a; done; echo "after: $a"'
111
222
after: 111
to
ksh -c 'a=111; echo foo | while read bar; do echo $a; a=222; echo $a; done; echo "after: $a"'
111
222
after: 222
Zsh gives the same result as ksh93.
Unfortunately, pdksh doesn't support process substitution and ksh93 does, but not when redirected into the done of a while loop, so the usual solution which works in Bash is not available. This is what it would look like:
# Bash (or Zsh)
while read ...
do
...
done < <(command)
Using a temporary file may be the only solution:
command > tmpfile
while read
do
...
done < tmpfile
Some additional notes:
Instead of cat ${CFG_FILE} | grep -v ^\# do grep -v ^\# "${CFG_FILE}"
Usually, you should use read -r so backslashes are handled literally
Instead of NAME=$(echo $CFG_FILE | cut -f1 -d\.) you should be able to do something like NAME=${CFG_FILE%%.*} and VALUE=${#*=}; VALUE=${VALUE%%=*}
Variables should usually be quoted on output, for example in each of your echo statements and your cat command
I recommend the habit of using lowercase or mixed case variable names to avoid conflict with shell variables (though none are present in your posted code)