In Bash, I'd do it this way:
[ -v IFS ] && oldIFS=$IFS || unset oldIFS
IFS=something
some commands
[ -v oldIFS ] && IFS=$oldIFS || unset IFS
In Bash, I'd do it this way:
[ -v IFS ] && oldIFS=$IFS || unset oldIFS
IFS=something
some commands
[ -v oldIFS ] && IFS=$oldIFS || unset IFS