add get_current_dir_name function

include/unistd.h

@@ -158,6 +158,7 @@ unsigned ualarm(unsigned, unsigned);
 int setgroups(size_t, const gid_t []);
 int setresuid(uid_t, uid_t, uid_t);
 int setresgid(gid_t, gid_t, gid_t);
+char *get_current_dir_name(void);
 #endif
 
 #define _XOPEN_VERSION          700

src/misc/get_current_dir_name.c

@@ -0,0 +1,12 @@
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include <unistd.h>
+
+char *get_current_dir_name(void) {
+	char buf[PATH_MAX];
+	char* res = getenv("PWD");
+	if(res && *res) return strdup(res);
+	if(!getcwd(buf, sizeof(buf))) return NULL;
+	return strdup(buf);
+}