diff --git a/src/bee-list.sh.in b/src/bee-list.sh.in
index 4d1b1f9..cbbb3a0 100644
--- a/src/bee-list.sh.in
+++ b/src/bee-list.sh.in
@@ -43,7 +43,7 @@ fi
 VERSION=${BEE_VERSION}
 
 : ${BEE_BINDIR:=@BINDIR@}
-: ${BEESORT:=sort}
+: ${BEESORT:=${BEE_BINDIR}/beesort}
 
 #
 # BUGS TO FIX/FEATURES TO ADD:
diff --git a/src/bee_tree.c b/src/bee_tree.c
index 64a5a47..53b6167 100644
--- a/src/bee_tree.c
+++ b/src/bee_tree.c
@@ -3,14 +3,15 @@
 #include <stdlib.h>
 #include <string.h>
 #include <assert.h>
+#include <errno.h>
 
 #include "bee_tree.h"
 
-static void *bee_tree_generate_key_default(void *data)
+static void *bee_tree_generate_key_default(const void *data)
 {
     assert(data);
 
-    return data;
+    return (void *)data;
 }
 
 static int bee_tree_compare_key_default(void *a, void *b)
@@ -240,7 +241,7 @@ static void bee_node_print(struct bee_tree *tree, struct bee_subtree *node, int
     assert(tree);
     assert(node);
 
-    assert(tree->print_key);
+    assert(tree->print || tree->print_key);
 
     for (i = 0 ; i < depth ; i++) {
         putchar('-');
@@ -252,13 +253,15 @@ static void bee_node_print(struct bee_tree *tree, struct bee_subtree *node, int
     if(dir < 0)
         putchar('/');
 
-    tree->print_key(node->key);
+    if (tree->print)
+        tree->print(node->key, node->data);
+    else
+        tree->print_key(node->key);
 
 #ifdef TREE_DEBUG
     printf(" [ h=%d bf=%d ]", node->height, node->balance_factor);
 #endif
 
-    putchar('\n');
 }
 
 static void bee_tree_balance_node(struct bee_tree *tree, struct bee_subtree *node)
@@ -318,6 +321,19 @@ static struct bee_subtree *bee_tree_insert_node(struct bee_tree *tree, struct be
     while (!node->parent) {
         cmp = tree->compare_key(node->key, current->key);
 
+        if ((cmp == 0) && (tree->flags & (BEE_TREE_FLAG_UNIQUE|BEE_TREE_FLAG_UNIQUE_DATA))) {
+            /* do not insert dupes */
+            if (!(tree->flags & BEE_TREE_FLAG_UNIQUE_DATA))
+                return NULL;
+
+            assert(tree->compare_data);
+
+            cmp = tree->compare_data(node->data, current->data);
+
+            if (cmp == 0)
+                return NULL;
+        }
+
         if (cmp < 0) {
             if (current->left) {
                 current = current->left;
@@ -352,6 +368,8 @@ struct bee_subtree *bee_tree_insert(struct bee_tree *tree, void *data)
 
     assert(tree->generate_key);
 
+    errno = 0;
+
     node = bee_subtree_allocate();
     if (!node)
         return NULL;
@@ -359,9 +377,21 @@ struct bee_subtree *bee_tree_insert(struct bee_tree *tree, void *data)
     node->data = data;
     node->key  = tree->generate_key(data);
 
-    bee_tree_insert_node(tree, node);
+    if (!node->key) {
+        free(node);
+        return NULL;
+    }
 
-    return node;
+    if(bee_tree_insert_node(tree, node))
+        return node;
+
+    if (tree->free_key)
+        tree->free_key(node->key);
+
+    free(node);
+
+    errno=EEXIST;
+    return NULL;
 }
 
 static struct bee_subtree *bee_tree_search_node_by_key(struct bee_tree *tree, void *key)
@@ -515,6 +545,32 @@ static void bee_subtree_print_plain(struct bee_tree *tree, struct bee_subtree *n
     bee_subtree_print_plain(tree, node->right);
 }
 
+int bee_tree_set_flags(struct bee_tree *tree, int flags)
+{
+    int oflags;
+
+    assert(tree);
+    assert(flags);
+
+    oflags = tree->flags;
+    tree->flags |= flags;
+
+    return oflags;
+}
+
+int bee_tree_unset_flags(struct bee_tree *tree, int flags)
+{
+    int oflags;
+
+    assert(tree);
+    assert(flags);
+
+    oflags = tree->flags;
+    tree->flags &= ~flags;
+
+    return oflags;
+}
+
 void bee_tree_print(struct bee_tree *tree)
 {
     assert(tree);
diff --git a/src/bee_tree.h b/src/bee_tree.h
index 39a88d8..d1aee66 100644
--- a/src/bee_tree.h
+++ b/src/bee_tree.h
@@ -5,13 +5,18 @@
 struct bee_tree {
     struct bee_subtree *root;
 
+    int flags;
+
     void   (*free_data)(void *data);
 
-    void * (*generate_key)(void *data);
-    void   (*free_key)(void *data);
+    void * (*generate_key)(const void *data);
+    void   (*free_key)(void *key);
 
     int    (*compare_key)(void *a, void *b);
+    int    (*compare_data)(void *a, void *b);
+
     void   (*print_key)(void *key);
+    void   (*print)(void *key, void *data);
 };
 
 struct bee_subtree {
@@ -29,6 +34,9 @@ struct bee_subtree {
 #define BEE_TREE_MAX(a,b)  (((a) > (b)) ? (a) : (b))
 #define BEE_TREE_HEIGHT(t) ((t) ? ((t)->height) : 0)
 
+#define BEE_TREE_FLAG_UNIQUE      (1<<0)
+#define BEE_TREE_FLAG_UNIQUE_DATA (1<<1)
+
 struct bee_tree *bee_tree_allocate(void);
 void bee_tree_free(struct bee_tree *tree);
 struct bee_subtree *bee_tree_insert(struct bee_tree *tree, void *data);
@@ -39,4 +47,7 @@ void *bee_tree_delete(struct bee_tree *tree, void *key);
 void bee_tree_print(struct bee_tree *tree);
 void bee_tree_print_plain(struct bee_tree *tree);
 
+int bee_tree_set_flags(struct bee_tree *tree, int flags);
+int bee_tree_unset_flags(struct bee_tree *tree, int flags);
+
 #endif
diff --git a/src/beesort.c b/src/beesort.c
index 8553a5c..c622c85 100644
--- a/src/beesort.c
+++ b/src/beesort.c
@@ -27,6 +27,7 @@
 #include <string.h>
 #include <limits.h>
 #include <getopt.h>
+#include <errno.h>
 
 #include "bee_version.h"
 #include "bee_version_compare.h"
@@ -35,22 +36,81 @@
 #include "bee_tree.h"
 #include "bee_getopt.h"
 
-void my_free_data(void *data)
+void my_free_key(void *key)
 {
-    struct beeversion *v = data;
+    struct beeversion *v = key;
 
     free(v->string);
     free(v);
 }
 
+void my_free_data(void *data)
+{
+    free(data);
+}
+
 int my_compare_key(void *a, void *b)
 {
     return compare_beepackages(a, b);
 }
 
-void my_print_key(void *key)
+int my_compare_data(void *a, void *b)
 {
-    print_format("%A", key, NULL);
+    return strcmp(a, b);
+}
+
+void my_print(void *key, void *data)
+{
+    fputs(data, stdout);
+}
+
+void *my_generate_key(const void *data)
+{
+    const char *line = data;
+    size_t l;
+    char *s, *p;
+    char *string;
+    struct beeversion *v;
+
+    string = strdup(line);
+
+    if(!string) {
+        perror("calloc(s)");
+        return NULL;
+    }
+
+    s = string;
+    l = strlen(s);
+    p = s+l-1;
+
+    while (p > s && (*p == ' ' || *p == '\t' || *p == '\n' || *p == '\r'))
+        *(p--) = 0;
+
+    while (*s && (*s == ' ' || *s == '\t'))
+        s++;
+
+    if(p < s) {
+        free(string);
+        errno = EINVAL;
+        return NULL;
+    }
+
+    v = calloc(1, sizeof(*v));
+    if(!v) {
+        perror("calloc(beeversion)");
+        free(s);
+        return NULL;
+    }
+
+    if(parse_version(s, v) != 0) {
+        free(v->string);
+        init_version(s, v);
+        v->pkgname = v->string;
+    }
+
+    free(string);
+
+    return v;
 }
 
 struct bee_tree *init_tree(void)
@@ -64,9 +124,12 @@ struct bee_tree *init_tree(void)
         exit(EXIT_FAILURE);
     }
 
-    tree->free_data   = &my_free_data;
-    tree->compare_key = &my_compare_key;
-    tree->print_key   = &my_print_key;
+    tree->generate_key = &my_generate_key;
+    tree->free_key     = &my_free_key;
+    tree->free_data    = &my_free_data;
+    tree->compare_key  = &my_compare_key;
+    tree->compare_data = &my_compare_data;
+    tree->print        = &my_print;
 
     return tree;
 }
@@ -74,15 +137,15 @@ struct bee_tree *init_tree(void)
 
 int main(int argc, char *argv[])
 {
-    char line[LINE_MAX], *s, *p;
+    char line[LINE_MAX];
+    char *data;
     FILE *file;
+
     struct bee_tree *tree;
-    struct beeversion *v;
+    struct bee_subtree *subtree;
 
     char *filename;
 
-    int l;
-
     int opt;
     int optindex;
     int optind;
@@ -107,10 +170,11 @@ int main(int argc, char *argv[])
 
         switch(opt) {
             case 'u':
-                opt_uniq = 1;
+                opt_uniq++;
                 break;
         }
     }
+
     optind = optctl.optind;
     argc   = optctl.argc;
     argv   = optctl.argv;
@@ -129,36 +193,33 @@ int main(int argc, char *argv[])
 
     tree = init_tree();
 
-    while(fgets(line, LINE_MAX, file)) {
-        l = strlen(line);
-        s = line;
-        p = line+l-1;
-
-        while (p > s && (*p == ' ' || *p == '\t' || *p == '\n' || *p == '\r'))
-            *(p--) = 0;
-
-        while (*s && (*s == ' ' || *s == '\t'))
-            s++;
+    if (opt_uniq == 1)
+        bee_tree_set_flags(tree, BEE_TREE_FLAG_UNIQUE_DATA);
+    else if (opt_uniq > 1)
+        bee_tree_set_flags(tree, BEE_TREE_FLAG_UNIQUE);
 
-        if(p < s)
-            continue;
-
-        v = calloc(1, sizeof(*v));
-        if(v == NULL) {
-            perror("cannot allocate memory ..");
+    while(fgets(line, LINE_MAX, file)) {
+        data = strdup(line);
+        if(!data) {
+            perror("strdup(data)");
             bee_tree_free(tree);
             fclose(file);
             exit(EXIT_FAILURE);
         }
 
-        if(parse_version(s, v) != 0) {
-            free(v->string);
-            init_version(s, v);
-            v->pkgname = v->string;
-        }
+        subtree = bee_tree_insert(tree, data);
+        if(subtree)
+            continue;
 
-        if(!(opt_uniq && bee_tree_search(tree, v)))
-            bee_tree_insert(tree, v);
+        if(errno == EINVAL)
+            continue;
+
+        if(errno == EEXIST)
+            continue;
+
+        bee_tree_free(tree);
+        fclose(file);
+        exit(EXIT_FAILURE);
     }
 
     fclose(file);