diff --git a/src/tools/gcns.c b/src/tools/gcns.c
index 59e594fa..7f05a20e 100644
--- a/src/tools/gcns.c
+++ b/src/tools/gcns.c
@@ -38,6 +38,7 @@
 #include <getopt.h>
 
 #include "common/compat_strlcpy.h"
+#include "gcns.h"
 #include "libopensc/asn1.h"
 #include "libopensc/cardctl.h"
 #include "libopensc/cards.h"
@@ -51,57 +52,92 @@ static int opt_wait = 0;
 static const char *opt_reader = NULL;
 static sc_context_t *ctx = NULL;
 static sc_card_t *card = NULL;
+sc_context_param_t ctx_param;
 
-static void die(int ret) {
-    if (card) {
-        sc_disconnect_card(card);
-    }
-    if (ctx) sc_release_context(ctx);
-    exit(ret);
-}
-
-int main(int argc, char *argv[]) {
+int gcns_init() {
     int r, err = 0;
-    sc_context_param_t ctx_param;
     int lcycle = SC_CARDCTRL_LIFECYCLE_ADMIN;
 
-    printf("OpenSC version: %s\n", sc_get_version());
-
     memset(&ctx_param, 0, sizeof(ctx_param));
     ctx_param.ver = 0;
 
     r = sc_context_create(&ctx, &ctx_param);
     if (r) {
         fprintf(stderr, "Failed to establish context: %s\n", sc_strerror(r));
-        return 1;
+        return GCNS_INIT;
     }
 
     ctx->flags |= SC_CTX_FLAG_ENABLE_DEFAULT_DRIVER;
 
     err = util_connect_card_ex(ctx, &card, opt_reader, opt_wait, 0, 0);
-    if (err) goto end;
+    if (err) {
+        return GCNS_INIT;
+    }
 
     r = sc_lock(card);
     if (r == SC_SUCCESS)
         r = sc_card_ctl(card, SC_CARDCTL_LIFECYCLE_SET, &lcycle);
     sc_unlock(card);
-    if (r && r != SC_ERROR_NOT_SUPPORTED)
-        printf("unable to change lifecycle: %s\n", sc_strerror(r));
+    if (r && r != SC_ERROR_NOT_SUPPORTED) {
+        fprintf(stderr, "unable to change lifecycle: %s\n", sc_strerror(r));
+        return GCNS_INIT;
+    }
 
-    u8 buffer[2048];
+    return GCNS_SUCCESS;
+}
+
+int gcns_close() {
+    if (card) {
+        sc_disconnect_card(card);
+    }
+    if (ctx) sc_release_context(ctx);
+    return GCNS_SUCCESS;
+}
+
+int gcns_read_personal_data(u8 *buffer, size_t len) {
     sc_path_t path;
+    int r;
+
     sc_format_path("3F0011001102", &path);
     r = sc_select_file(card, &path, NULL);
     if (r) {
-        fprintf(stderr, "no select file 3F0011001102\n");
+        fprintf(stderr, "no select file: 3F0011001102\n");
+        return GCNS_READ_PERSONAL_DATA;
     }
     r = sc_read_binary(card, 0, buffer, 0x180, 0);
-    if (r) {
+    if (r < 0) {
         fprintf(stderr, "no read binary: %d\n", r);
+        return GCNS_READ_PERSONAL_DATA;
     }
-    util_hex_dump_asc(stdout, buffer, r, 0);
-end:
-    die(err);
 
-    return 0; /* not reached */
+    return r;
+}
+
+int main(int argc, char *argv[]) {
+    int r;
+
+    printf("OpenSC version: %s\n", sc_get_version());
+
+    r = gcns_init();
+    if (r != GCNS_SUCCESS) {
+        fprintf(stderr, "Init Error\n");
+        return GCNS_INIT;
+    }
+
+    u8 buffer[2048];
+    r = gcns_read_personal_data(buffer, 2048);
+
+    if (r < 0) {
+        fprintf(stderr, "Read personal data error\n");
+        return GCNS_READ_PERSONAL_DATA;
+    }
+
+    util_hex_dump_asc(stdout, buffer, r, 0);
+
+    r = gcns_close();
+    if (r != GCNS_SUCCESS) {
+        return GCNS_CLOSE;
+    }
+
+    return GCNS_SUCCESS;
 }
diff --git a/src/tools/gcns.h b/src/tools/gcns.h
new file mode 100644
index 00000000..854a8e58
--- /dev/null
+++ b/src/tools/gcns.h
@@ -0,0 +1,9 @@
+#ifndef GCNS_H
+#define GCNS_h
+
+#define GCNS_SUCCESS 0
+#define GCNS_INIT -1001
+#define GCNS_READ_PERSONAL_DATA -1002
+#define GCNS_CLOSE -1003
+
+#endif