diff --git a/src/example/example.c b/src/example/example.c
new file mode 100644
index 0000000..640b405
--- /dev/null
+++ b/src/example/example.c
@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include "../log.h"
+
+extern const char *level_strings[];
+
+void callback1(log_Event *ev)
+{
+    char logline[128];
+    snprintf(logline, 128, "%-5s %s:%d: ",
+        level_strings[ev->level], ev->file, ev->line);
+    vsnprintf(logline, 128, ev->fmt, ev->ap);
+    printf("%s: %s\n", __func__, logline);
+}
+
+void callback2(log_Event *ev)
+{
+    char logline[128];
+    snprintf(logline, 128, "%-5s %s:%d: ",
+        level_strings[ev->level], ev->file, ev->line);
+    vsnprintf(logline, 128, ev->fmt, ev->ap);
+    printf("%s: %s\n", __func__, logline);
+}
+
+int main()
+{
+    log_trace("hello");
+    log_debug("hello");
+    log_info("hello");
+    log_warn("hello");
+    log_error("hello");
+    log_fatal("hello");
+    log_debug("============== update loglevel to FATAL =============");
+    log_set_level(LOG_FATAL);
+    log_trace("hello");
+    log_debug("hello");
+    log_info("hello");
+    log_warn("hello");
+    log_error("hello");
+    log_fatal("hello");
+    log_debug("===================== init log =====================");
+    log_add_callback(callback1, "progname", LOG_TRACE);
+    log_add_callback(callback2, "progname", LOG_TRACE);
+    log_trace("hello");
+    log_debug("hello");
+    log_info("hello");
+    log_warn("hello");
+    log_error("hello");
+    log_fatal("hello");
+    log_debug("============ update loglevels of callbacks ========");
+    log_set_level_callback(callback1, LOG_FATAL);
+    log_set_level_callback(callback2, LOG_WARN);
+    return 0;
+}
\ No newline at end of file
diff --git a/src/log.c b/src/log.c
index 1a7626e..f25f095 100644
--- a/src/log.c
+++ b/src/log.c
@@ -39,7 +39,7 @@ static struct {
 } L;
 
 
-static const char *level_strings[] = {
+const char *level_strings[] = {
   "TRACE", "DEBUG", "INFO", "WARN", "ERROR", "FATAL"
 };
 
@@ -122,6 +122,17 @@ int log_add_callback(log_LogFn fn, void *udata, int level) {
   return -1;
 }
 
+int log_set_level_callback(log_LogFn fn, int level) {
+  for (int i = 0; i < MAX_CALLBACKS; i++) {
+    if (L.callbacks[i].fn == fn) {
+      L.callbacks[i].level = level;
+      return 0;
+    }
+  }
+  return -1;
+}
+
+
 
 int log_add_fp(FILE *fp, int level) {
   return log_add_callback(file_callback, fp, level);
diff --git a/src/log.h b/src/log.h
index b1fae24..c9fc906 100644
--- a/src/log.h
+++ b/src/log.h
@@ -42,6 +42,7 @@ void log_set_lock(log_LockFn fn, void *udata);
 void log_set_level(int level);
 void log_set_quiet(bool enable);
 int log_add_callback(log_LogFn fn, void *udata, int level);
+int log_set_level_callback(log_LogFn fn, int level);
 int log_add_fp(FILE *fp, int level);
 
 void log_log(int level, const char *file, int line, const char *fmt, ...);