diff --git a/lib.nas b/lib.nas
index 44ae13e..77cbf0f 100644
--- a/lib.nas
+++ b/lib.nas
@@ -202,9 +202,7 @@ var values=func(hash){
 # println has the same function as print.
 # but it will output a '\n' after using print.
 var println=func(elems...){
-    __builtin_print(elems);
-    elems=['\n'];
-    return __builtin_print(elems);
+    return __builtin_println(elems);
 }
 
 var isfunc=func(f){
diff --git a/makefile b/makefile
index 30cdd01..09d21d4 100644
--- a/makefile
+++ b/makefile
@@ -34,6 +34,7 @@ test:nasal
 	-@ ./nasal -op -t -d -o test/md5compare.nas
 	-@ ./nasal -op -d test/module_test.nas
 	@ ./nasal -op -e test/nasal_test.nas
+	@ ./nasal -op -c test/occupation.nas
 	@ ./nasal -op -t -d test/pi.nas
 	@ ./nasal -op -t -d test/prime.nas
 	@ ./nasal -op -e test/qrcode.nas
diff --git a/nasal_builtin.h b/nasal_builtin.h
index 091b37f..937d4b6 100644
--- a/nasal_builtin.h
+++ b/nasal_builtin.h
@@ -10,6 +10,7 @@
 // to add new builtin function, declare it here and write the definition below
 #define nas_native(name) nasal_ref name(nasal_ref*,nasal_gc&)
 nas_native(builtin_print);
+nas_native(builtin_println);
 nas_native(builtin_abort);
 nas_native(builtin_append);
 nas_native(builtin_setsize);
@@ -114,6 +115,7 @@ struct
 } builtin[]=
 {
     {"__builtin_print",   builtin_print   },
+    {"__builtin_println", builtin_println },
     {"__builtin_abort",   builtin_abort   },
     {"__builtin_append",  builtin_append  },
     {"__builtin_setsize", builtin_setsize },
@@ -205,13 +207,9 @@ struct
     {nullptr,             nullptr         }
 };
 
-nasal_ref builtin_print(nasal_ref* local,nasal_gc& gc)
+inline void print_core(std::vector<nasal_ref>& elems)
 {
-    // get arguments
-    // local[0] is reserved for 'me'
-    nasal_ref vec=local[1];
-    // main process
-    for(auto& i:vec.vec().elems)
+    for(auto& i:elems)
         switch(i.type)
         {
             case vm_none: std::cout<<"null";           break;
@@ -224,10 +222,25 @@ nasal_ref builtin_print(nasal_ref* local,nasal_gc& gc)
             case vm_obj:  std::cout<<"<object>";       break;
             case vm_co:   std::cout<<"<coroutine>";    break;
         }
+}
+nasal_ref builtin_print(nasal_ref* local,nasal_gc& gc)
+{
+    // get arguments
+    // local[0] is reserved for 'me'
+    nasal_ref vec=local[1];
+    // main process
+    print_core(vec.vec().elems);
     std::cout<<std::flush;
     // generate return value
     return nil;
 }
+nasal_ref builtin_println(nasal_ref* local,nasal_gc& gc)
+{
+    nasal_ref vec=local[1];
+    print_core(vec.vec().elems);
+    std::cout<<std::endl;
+    return nil;
+}
 nasal_ref builtin_abort(nasal_ref* local,nasal_gc& gc)
 {
     std::abort();
diff --git a/stl/lib.nas b/stl/lib.nas
index 44ae13e..77cbf0f 100644
--- a/stl/lib.nas
+++ b/stl/lib.nas
@@ -202,9 +202,7 @@ var values=func(hash){
 # println has the same function as print.
 # but it will output a '\n' after using print.
 var println=func(elems...){
-    __builtin_print(elems);
-    elems=['\n'];
-    return __builtin_print(elems);
+    return __builtin_println(elems);
 }
 
 var isfunc=func(f){
diff --git a/test/calc.nas b/test/calc.nas
index a15d2f4..93323eb 100644
--- a/test/calc.nas
+++ b/test/calc.nas
@@ -1,16 +1,16 @@
 var source=[
     "main.cpp              ",
-    "nasal_err.h           ",
     "nasal_ast.h           ",
     "nasal_builtin.h       ",
     "nasal_codegen.h       ",
-    "nasal_opt.h           ",
+    "nasal_dbg.h           ",
+    "nasal_err.h           ",
     "nasal_gc.h            ",
     "nasal_import.h        ",
     "nasal_lexer.h         ",
+    "nasal_opt.h           ",
     "nasal_parse.h         ",
     "nasal_vm.h            ",
-    "nasal_dbg.h           ",
     "nasal.h               "
 ];
 
@@ -55,6 +55,7 @@ var testfile=[
     "test/md5compare.nas   ",
     "test/module_test.nas  ",
     "test/nasal_test.nas   ",
+    "test/occupation.nas   ",
     "test/pi.nas           ",
     "test/prime.nas        ",
     "test/qrcode.nas       ",
diff --git a/test/md5compare.nas b/test/md5compare.nas
index 69ce187..9f64c98 100644
--- a/test/md5compare.nas
+++ b/test/md5compare.nas
@@ -86,6 +86,7 @@ var filechecksum=func(){
         "./test/md5compare.nas   ",
         "./test/module_test.nas  ",
         "./test/nasal_test.nas   ",
+        "./test/occupation.nas   ",
         "./test/pi.nas           ",
         "./test/prime.nas        ",
         "./test/qrcode.nas       ",
diff --git a/test/occupation.nas b/test/occupation.nas
new file mode 100644
index 0000000..705f391
--- /dev/null
+++ b/test/occupation.nas
@@ -0,0 +1,50 @@
+var cpu_stat=func(){
+    var cpu=split("\n",io.fin("/proc/stat"))[0];
+    cpu=split(" ",cpu);
+    cpu={
+        name:cpu[0],
+        user:cpu[1],
+        nice:cpu[2],
+        system:cpu[3],
+        idle:cpu[4],
+        iowait:cpu[5],
+        irq:cpu[6],
+        softirq:cpu[7],
+    };
+    return cpu;
+}
+var cpu_occupation=func(){
+    var cpu0=cpu_stat();
+    unix.sleep(1);
+    var cpu1=cpu_stat();
+    var t0=cpu0.user+cpu0.nice+cpu0.system+cpu0.idle+cpu0.iowait+cpu0.irq+cpu0.softirq;
+    var t1=cpu1.user+cpu1.nice+cpu1.system+cpu1.idle+cpu1.iowait+cpu1.irq+cpu1.softirq;
+    var interval=cpu1.idle-cpu0.idle;
+    return t0==t1?0:(1-interval/(t1-t0))*100;
+}
+
+var mem_occupation=func(){
+    var meminfo=split("\n",io.fin("/proc/meminfo"));
+    var mem_res={};
+    forindex(var i;meminfo){
+        var tmp=split(" ",meminfo[i])[0:1];
+        tmp[0]=substr(tmp[0],0,size(tmp[0])-1);
+        mem_res[tmp[0]]=num(tmp[1]);
+    }
+    return mem_res;
+}
+func(){
+    if(os.platform()=="windows"){
+        println("haven't supported yet.");
+        return;
+    }
+    while(1){
+        var mem=mem_occupation();
+        var mem_occ=(mem.MemTotal-mem.MemFree)/mem.MemTotal*100;
+        var cpu_occ=cpu_occupation();
+        println("CPU occupation(%)   : ",cpu_occ>90?"\e[91m":"\e[32m",cpu_occ,"\e[0m");
+        println("Memory total(GB)    : \e[36m",mem.MemTotal/1024/1024,"\e[0m");
+        println("Memory free(GB)     : \e[36m",mem.MemFree/1024/1024,"\e[0m");
+        println("Memory occupation(%): ",mem_occ>30?"\e[91m":"\e[32m",mem_occ,"\e[0m");
+    }
+}();
\ No newline at end of file