arch/um/sys-x86_64/vdso/checkundef.sh

#!/bin/sh
nm="$1"
file="$2"
$nm "$file" | grep '^ *U' > /dev/null 2>&1
if [ $? -eq 1 ]; then
    exit 0
else
    echo "$file: undefined symbols found" >&2
    exit 1
fi