+# Try to expand variables in a path definition, discarding it if expansion fails.
+function expandpath() {
+ local path="$1"; shift
+
+ while [ -n "$path" ]; do
+ [ "${path/\$/}" = "$path" ] && return 0
+ path="${path#*\$}"
+
+ local var="${path%%/*}"
+ eval "[ -n \"\$$var\" ] || return 1"
+ done
+
+ return 0
+}
+
+# Helper.
+function addpath() {
+ local path="$1"; shift
+ local dir="$1"; shift
+
+ if ! expandpath "$dir"; then
+ echo "$path"
+ else
+ dir=$(eval echo "$dir")
+ if [ -d "$dir" ]; then
+ echo "$path:$dir"
+ else
+ echo "$path"
+ fi
+ fi
+}
+