Return to Answer

In Bash, I'd do it this way:

[ -v IFS ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ -v oldIFS ] && IFS="$oldIFS" 

or this way:

[ "${IFS+set}" ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ "${oldIFS+set}" ] && IFS="$oldIFS" 

In Bash, I'd do it this way:

[ -v IFS ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ -v oldIFS ] && IFS="$oldIFS" || unset IFS 

or this way:

[ "${IFS+set}" ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ "${oldIFS+set}" ] && IFS="$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 

or this way:

[ "${IFS+set}" ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ "${oldIFS+set}" ] && IFS="$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" 

or this way:

[ "${IFS+set}" ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ "${oldIFS+set}" ] && IFS="$oldIFS" 

In Bash, I'd do it this way:

[ -v IFS ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ -v oldIFS ] && IFS="$oldIFS" || unset IFS 

this may be better:

[ "${IFS+set}" ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ "${oldIFS+set}" ] && IFS="$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 

or this way:

[ "${IFS+set}" ] && oldIFS="$IFS" || unset oldIFS IFS=something some commands [ "${oldIFS+set}" ] && IFS="$oldIFS" || unset IFS