Pour utiliser la sortie de ldapsearch en entrée de ldapdelete :

ldapsearch -Y EXTERNAL -H ldapi:/// -LLL -tt -b dc=example,dc=com "(attr=*)" "dn"  | \
awk '{gsub("dn: ", "");print}' | \
tr "[:upper:]" "[:lower:]" | \
sed -n 'H; ${ x; s/\n//; s/\n //g; p}' | \
ldapdelete -f - -Y EXTERNAL -H ldapi:///