Display a Digital Clock

Question

Display a Digital Clock

(I see there are many clock challenges, I have tried to read them all, I'm pretty sure this is unique)

Write some code that continuously updates a digital clock displayed in the format h:m:s where h, m, and s can occupy 1 or 2 characters each. The restrictions in simple terms as @BlueEyedBeast put it, I basically want it to replace the time shown.

• Newlines are not allowed
• Trailing spaces are allowed
• Other trailing characters are not allowed
• No seconds should be missed (57 -> 59 is not allowed)
• Numbers beginning with "0" are allowed, as long as they don't occupy more than 2 characters
• The code must not accept any input
• If your language can't get the current time without input, you may use for input up to 8 bytes in a standardly allowed way
• Output must be to stdout
• This is codegolf so the shortest answer wins!

Example

I'm working on a language named *><> (starfish) because programs like this aren't possible in ><> (just wait for file i/o) . Here's a working digital clock program in it (ungolfed). This program is written in *><>:

s":"m":"hnonon"   "ooo88888888888ooooooooooo1S

^{Note: Everything is identical to ><> in this except, s = second, m = minute, h = hour, S = sleep(100ms*x)}

This outputs:

14:44:31

Updating every 100ms until terminated.

Disallowed Examples

The following are not allowed:

1:

14:44:3114:44:32

2:

14:44:31 14:44:32

3:

14:44:31
14:44:32

The time must remain on the first line it was outputted with no visible trailing characters. Clearing the terminal though, would be allowed as that still wouldn't have any trailing characters.

Answer 1

HTML + JS (ES6), 8 + 60 = 68 bytes

Tested in Chrome.

setInterval`a.innerHTML=new Date().toLocaleTimeString('fr')`

<a id=a>

-1 byte (@ETHProductions): Use French time format instead of .toTimeString().slice(0,8)

---

HTML + JS (ES6), 8 + 62 = 70 bytes

This will work in FireFox.

setInterval('a.innerHTML=new Date().toLocaleTimeString`fr`',0)

<a id=a>

-3 bytes (@ETHProductions): Use French time format instead of .toTimeString().slice(0,8)

Answer 2

Python 2, 50 bytes

(Python 2.1+ for ctime with no argument)

import time
while 1:print'\r'+time.ctime()[11:19],

time.ctime() yields a formatted string, from which the hh:mm:ss may be sliced using [11:19] (it remains in the same location whatever the date and time).

printing the carriage return '\r' before the text and making the text the first item of a tuple with , effectively suppresses the implicit trailing '\n' and overwrites the previously written output.

while 1 loops forever.

Answer 3

Mathematica, 48 41 37 28 bytes

Do[s=Now[[2]],∞]~Monitor~s

The output will be a TimeObject, refreshing continuously.

Looks like this:

Alternative versions

48 bytes:

Dynamic@Refresh[TimeObject[],UpdateInterval->.1]

53 bytes:

Dynamic@Refresh[DateString@"Time",UpdateInterval->.1]

Answer 4

Pyke, 6 bytes

Ctr\ J

Try it here!

I think this is valid. Replace the space character with carriage return for valid output (does not work online)

Answer 5

I see that the requirement for a non-signal UI input to stop the program has been removed. So now we can do:

Bash + coreutils, 28

yes now|date -f- +$'\e[2J'%T

yes continuously outputs the string "now", once per line, into a pipe.

date -f- reads interprets each "now" as the current time, then outputs in the required format. The format string includes the ANSI escape sequence to clear the screen. date does output a newline after the date - I'm not sure if this disqualifies, since the screen is cleared every time anyway.

If it disqualifies, then we can use tr instead:

Bash + coreutils, 31

yes now|date -f- +%T|tr \\n \\r

---

Previous Answers:

Bash + X, 32

xclock -d -update 1 -strftime %T

Unfortunately this can only update every second. If that disqualifies, then we can do this instead:

Bash + coreutils, 43

until read -t0
do printf `date +%T`\\r
done

Answer 6

QBIC, 6 bytes

{_C?_d

{      Starts a DO-loop
 _C    CLS
   ?   PRINT
    _d TIME$

Constantly clears the screen and prints the system time in the format 22:03:41.

Answer 7

Clojure, 150 136 141 bytes

V3: 141 bytes :(

+5 bytes to fix a bug. Since the times aren't zero padded, the clock can "shrink" and expand when the time changes. It was "smearing" when it shrunk because the last digit was no longer being cleared. Fixed it by adding some spaces at the end to ensure everything is being overwritten.

#(while true(flush)(print(str(apply str(repeat 9"\b"))(.format(java.text.SimpleDateFormat."H:m:s")(java.util.Date.))"   "))(Thread/sleep 99))

V2: 136 bytes

#(while true(flush)(print(str(apply str(repeat 9"\b"))(.format(java.text.SimpleDateFormat."H:m:s")(java.util.Date.))))(Thread/sleep 99))

-14 bytes by switching to using SimpleDateFormat to format the date. Still huge.

V1: 150 bytes

#(while true(let[d(java.util.Date.)](flush)(print(str(apply str(repeat 9 "\b"))(.getHours d)":"(.getMinutes d)":"(.getSeconds d)))(Thread/sleep 100)))

I realized I'm probably using the worst way possible to get the date. Definitely room for improvement here.

Ungolfed:

(defn -main []
  (while true
    (let [d (java.util.Date.)]
      (flush)
      (print
        (str
          (apply str (repeat 9 "\b"))
          (.getHours d)":"(.getMinutes d)":"(.getSeconds d)))
      (Thread/sleep 100))))

Answer 8

C, 134 116 89 80 76 75 73 bytes

main(n){for(;time(&n);)printf("\r%02d:%02d:%02d",n/3600%24,n/60%60,n%60);}

---- Old versions:
main(n){for(;;)n=time(0),printf("\r%02d:%02d:%02d",n/3600%24,n/60%60,n%60);}

n;main(){for(;;)n=time(0),printf("\r%02d:%02d:%02d",n/3600%24,n/60%60,n%60);}

---- 

n;main(){for(;;)n=time(0),printf("\r%02d:%02d:%02d",n/3600%24,n/60%60,n%60);}

----

Saved 9 more bytes thanks to @nmjcman101 again:
n;main(){for(;;)n=time(0),printf("\r%02d:%02d:%02d",(n/3600)%24,(n/60)%60,n%60);}

----

Saved 27 bytes thanks to @nmjcman101
n,b[9];main(){for(;;){n=time(0);strftime(b,9,"%H:%M:%S",localtime(&n));printf("\r%s",b);}}

----

I figured out I don't need to put `#include<stdio.h>` into the file :)
#include<time.h>
main(){for(;;){time_t n=time(0);char b[9];strftime(b,9,"%H:%M:%S",localtime(&n));printf("\r%s",b);}}

----

#include<time.h>
#include<stdio.h>
main(){for(;;){time_t n=time(0);char b[9];strftime(b,9,"%H:%M:%S",localtime(&n));printf("\r%s",b);}}

Answer 9

Bash + watch, 19 bytes

watch is not a part of coreutils, but is available out of the box on virtually every Linux distro.

Golfed

watch -tn1 date +%T

Try it online !

Answer 10

WinDbg, 73 bytes

.do{r$t0=0;.foreach(p {.echotime}){r$t0=@$t0+1;j8==@$t0'.printf"p \r"'}}1

It continually updates a line with the current time until the user presses Ctrl+Break.

How it works:

.do                          * Start do-while loop
{
    r$t0 = 0;                * Set $t0 = 0
    .foreach(p {.echotime})  * Foreach space-delimited word in a sentence like "Debugger (not 
    {                        * debuggee) time: Mon Dec  5 14:08:10.138 2016 (UTC - 8:00)"
        r$t0 = @$t0+1;       * Increment $t0
        j 8==@$t0            * If $t0 is 8 (ie- p is the current time)
        '
            .printf"p \r"    * Print p (current time) and \r so the next print overwrites
        '
    }
} 1                          * Do-while condition: 1, loop forever

Sample output (well, you get the idea):

0:000> .do{r$t0=0;.foreach(p {.echotime}){r$t0=@$t0+1;j8==@$t0'.printf"p \r"'}}1
14:10:12.329

Answer 11

PHP, 28 bytes

for(;;)echo date("\rH:i:s");

The date function prints everything literally that it doesn´t recognize.

\r is the carriage return, sets the cursor to the first column.

Run with -r.

Answer 12

C#, 82 bytes

()=>{for(;;)Console.Write(new string('\b',8)+DateTime.Now.ToString("HH:mm:ss"));};

Anonymous method which constantly overwrites 8 characters with new output. Can be made 1 byte shorter if modifying to accept a dummy parameter (z=>...).

Full program:

using System;

public class Program
{
    public static void Main()
    {
        Action a =
        () =>
        {
            for (;;)
                Console.Write(new string('\b', 8) + DateTime.Now.ToString("HH:mm:ss"));
        };

        a();
    }
}

Answer 13

C#, 65 bytes

()=>{for(;;)Console.Write("\r"+DateTime.Now.ToLongTimeString());};

Works by overwriting the same line within an endless loop

Answer 14

SmileBASIC 3.3.2, 38 bytes

@L?TIME$;" ";
GOTO@L

UTF-16 sucks :(

Anyway, this repeatedly prints the local time in HH:MM:SS with a space after it, no newline afterward. It doesn't update every second though, it just repeatedly prints forever.

Answer 15

Powershell, 39 bytes

for(){write-host -n(date -F h:m:s`0`r)}

Because I dislike using cls in Powershell. From briantist's post @https://codegolf.stackexchange.com/a/102450/63383

Answer 16

Pascal, 61 bytes

uses sysutils;begin while 1=1do write(#13,timetostr(now))end.

Free pascal has nice time routines in SysUtils unit. Ungolfed:

uses
  sysutils;
begin
  while 1=1 do
    write(#13, timetostr(now));
end.

Answer 17

MATL, 11 bytes

`XxZ'13XODT

Infinite loop that clears the screen and prints the time in the specified format.

You can try it at MATL Online!. This compiler is experimental; if it doesn't work refresh the page and press "Run" again.

Answer 18

Vim, 26 bytes

qqS<C-r>=strftime("%T")<CR><esc>@qq@q

This creates a recursive macro (e.g. an eternal loop) that deletes all the text on the current line and replaces it with the current time.

Answer 19

Pyth - 28 bytes

Kinda longish, because pyth has no strftime.

#p+"\r"j\:m.[`02`dP>4.d2.d.1

Answer 20

Groovy, 45 characters

for(;;)print(new Date().format("\rHH:mm:ss"))

Answer 21

Jelly, 8 bytes

13Ọ7ŒTȮß

13Ọ        chr(13), carriage return
   7ŒT     time string, which extends the previous character
      Ȯ    print
       ß   call the whole link again

Try it online!

The carriage return doesn't work online, and I can't get the interpreter to work, so its kinda untested, but it works as expected when I use printable characters in place of the CR.

Answer 22

ForceLang, 123 bytes

def s set
s d datetime
s z string.char 8
s z z.repeat 16
label 1
io.write z
io.write d.toTimeString d.now()
d.wait 9
goto 1

datetime.toTimeString is backed in the reference implementation by Java's DateFormat.getTimeInstance(), which is locale-dependent, so you can set your default system locale to one that uses 24-hour time.

Answer 23

PowerShell, 30 28 24 20 bytes

Changed my computer's region to Germany based on raznagul's comment to save 4 bytes. :)

for(){date -F T;cls}

Previous version that works in all locales.

for(){date -F h:m:s;cls}

Answer 24

tcl, 69 bytes

while 1 {puts -nonewline \r[clock format [clock seconds] -format %T]}

Try it here!

Answer 25

C 65 (prev 64) bytes

Guaranteed to work on Linux machine. :)

@Marco Thanks!

f(){while(1){system("date +%T");usleep(100000);system("clear");}}

Answer 26

Batch, 36 bytes

@set/p.=␈␈␈␈␈␈␈␈%time:~0,8%<nul
@%0

Where ␈ represents the ASCII BS character (code 8).

Answer 27

Racket, 71 bytes

(require srfi/19)(let l()(display(date->string(current-date)"↵~3"))(l))

Where the ↵ is actually a CR (hex 0d). Hex dump of the program for further clarification (notice byte at position hex 4d):

00000000  28 72 65 71 75 69 72 65  20 73 72 66 69 2f 31 39  |(require srfi/19|
00000010  29 28 6c 65 74 20 6c 28  29 28 64 69 73 70 6c 61  |)(let l()(displa|
00000020  79 28 64 61 74 65 2d 3e  73 74 72 69 6e 67 28 63  |y(date->string(c|
00000030  75 72 72 65 6e 74 2d 64  61 74 65 29 22 0d 7e 33  |urrent-date)".~3|
00000040  22 29 29 28 6c 29 29                              |"))(l))|
00000047

Uses SRFI/19 included with the Racket distribution. (current-date) gets the current local date & time. The date->string format ~3 is ISO-8601 hour-minute-second format. (let l () ... (l)) in an idiomatic infinite loop. (require srfi/19) loads the srfi/19 module.

Answer 28

C, 156 bytes

#include<stdio.h>
#include<time.h>
int main(){time_t a;struct tm *b;char c[9];for(;;){time(&a);b=localtime(&a);strftime(c,9,"%H:%M:%S",b);printf("%s\r",c);}}

Answer 29

TI-Basic, 40 Bytes

(In TI-BASIC, many characters are 2 byte tokens, and colons at the beginning of a line are 0 extra bytes)

:ClrHome
:Output(1,6,":
:setTmFmt(24
:While 1
:Output(1,1,getTmSrr(0
:getTime
:Output(1,7,Ans(3
:End

Answer 30

R, 41 bytes

repeat{cat(format(Sys.time(),"%T"),"\r")}

Has one trailing space (because of cat default separator being a space).
Because of the refresh rate of the R GUI, running this in the GUI will occasionally skip some seconds, but if you save it to a file and run it on the command line it will display correctly every single seconds.
Will run forever until user interrupt.