1 files changed, 20 insertions, 3 deletions

diff --git a/libbb/compare_string_array.c b/libbb/compare_string_array.c
index 43c59e8e0..599449fe0 100644
--- a/libbb/compare_string_array.c
+++ b/libbb/compare_string_array.c
@@ -53,19 +53,24 @@ int FAST_FUNC index_in_substr_array(const char *const string_array[], const char
 
 int FAST_FUNC index_in_substrings(const char *strings, const char *key)
 {
-        int len = strlen(key);
+        int matched_idx = -1;
+        const int len = strlen(key);
 
         if (len) {
                 int idx = 0;
                 while (*strings) {
                         if (strncmp(strings, key, len) == 0) {
-                                return idx;
+                                if (strings[len] == '\0')
+                                        return idx; /* exact match */
+                                if (matched_idx >= 0)
+                                        return -1; /* ambiguous match */
+                                matched_idx = idx;
                         }
                         strings += strlen(strings) + 1; /* skip NUL */
                         idx++;
                 }
         }
-        return -1;
+        return matched_idx;
 }
 
 const char* FAST_FUNC nth_string(const char *strings, int n)
@@ -76,3 +81,15 @@ const char* FAST_FUNC nth_string(const char *strings, int n)
         }
         return strings;
 }
+
+#ifdef UNUSED_SO_FAR /* only brctl.c needs it yet */
+/* Returns 0 for no, 1 for yes or a negative value on error.  */
+smallint FAST_FUNC yesno(const char *str)
+{
+        static const char no_yes[] ALIGN1 =
+                "0\0" "off\0" "no\0"
+                "1\0" "on\0" "yes\0";
+        int ret = index_in_substrings(no_yes, str);
+        return ret / 3;
+}
+#endif