Output the Current Time

Question

Challenge

You must output the current time continuously (until cancelled by an interrupt), once every second, by any of the following means:

• It must be in 24-hour or AM/PM format.
  • If it is the former, it must be spaced out with colons (i.e. 15:47:36).
  • If it is the latter, it must be spaced out with colons and have the AM/PM following (i.e. 3:47:36 PM)
• It may be pulled from the internet.
• It may be the system time.
• It must output any naturally accessible form of output which supports text that you choose.
• Output may have extra information aside of the time in it, but you must guarantee one, and only one, output of time per second.
• The continuous output must be a second apart - if you choose to wait until the second changes between outputs, that is fine. If you wait a second between each output, that is perfectly acceptable, despite the eventual loss of accuracy.

Since this is a catalog, languages created after this challenge are allowed to compete. Note that there must be an interpreter so the submission can be tested. It is allowed (and even encouraged) to write this interpreter yourself for a previously unimplemented language. Other than that, all the standard rules of code-golf must be obeyed. Submissions in most languages will be scored in bytes in an appropriate preexisting encoding (usually UTF-8).

Catalog

The Stack Snippet at the bottom of this post generates the catalog from the answers a) as a list of shortest solution per language and b) as an overall leaderboard.

To make sure that your answer shows up, please start your answer with a headline, using the following Markdown template:

## Language Name, N bytes

where N is the size of your submission. If you improve your score, you can keep old scores in the headline, by striking them through. For instance:

## Ruby, <s>104</s> <s>101</s> 96 bytes

If there you want to include multiple numbers in your header (e.g. because your score is the sum of two files or you want to list interpreter flag penalties separately), make sure that the actual score is the last number in the header:

## Perl, 43 + 2 (-p flag) = 45 bytes

You can also make the language name a link which will then show up in the snippet:

## [><>](http://esolangs.org/wiki/Fish), 121 bytes

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Answer 1

Rebol, 25 bytes

forever[print now wait 1]

This prints day & time (24 hour HH:MM:SS). For an extra 5 bytes you can make it print just the time: forever[print now/time wait 1]

Answer 2

Batch (Windows), 21 bytes

t.bat

echo %time%
timeout 1
t

Shows the time, delays for 1 second, then recursively calls itself. This is run as t.bat in the same directory.

Answer 3

MATL, 11 bytes

`Z'0XOD1Y.T

Try it here.

Explanation

`         % do...while loop
  Z'      %   get current date and time  
  0XO     %   string representation of date and time, with format 'dd-mmm-yyyy HH:MM:SS'
  D       %   convert to string and display           
  1Y.     %   pause for 1 second
  T       %   push "true" value as loop condition to create infinite loop
          % implicitly end loop

Answer 4

QBasic, 16 bytes

Shamelessly stole (and imporoved upon) Mauris' design:

CLS:?TIME$:RUN

---

Previous version: 24 bytes

EDIT: Only just saw that I don't have to SLEEP 1 if I continuously clear the screen and print the time. That's 4 bytes shorter:

DO:CLS:PRINT TIME$:LOOP

---

Previous entry (28 bytes)

DO:PRINT TIME$:SLEEP 1:LOOP

Nothing fancy, not too shabby.

Answer 5

Pascal, 144 B

This program requires a processor complying to the ISO standard 10206 “Extended Pascal”, e. g. the GNU Pascal Compiler (GPC). It’s doing a busy wait until the time changes. The second line of the entire output will probably be printed in significantly less than a 1 second interval.

program t(output);var t:timeStamp;s:string(8);begin s:='';repeat getTimeStamp(t);if s<>time(t)then begin s:=time(t);writeLn(s)end until 6=9 end.

The code does not check timeStamp.timeValid, so on a system without a clock this program will print just a single line representing midnight, getTimeStamp’s default value if timeStamp.timeValid is set to false.

The return value of time is implementation-defined. It may be in an AM/PM format, military time, or something else. Thus it’s not guaranteed that the challenge’s specifications are met. At any rate, the GPC’s implementation returns something in the style of 22:00:42. This fits into a string(8). A different Pascal implementation may require more characters in order to detect a change in time.

Also, if you don’t mind a preceding empty line, you can use this 134 B program:

program t(output);var x:timeStamp;s:string(8);begin s:='';repeat getTimeStamp(x);if s<>time(x)then writeLn(s);s:=time(x)until 6=9 end.

Answer 6

TI-BASIC, 29 bytes

While 1
Output(1,1,getTimeStr(24)+":
Output(1,7,sum(getTime,3
End

TI-BASIC has a built-in getTimeStr, but it doesn't display seconds! How to fix this? Just display the seconds over the empty space after the minutes. (It would be much easier if there were a way to convert numbers to strings.)

Outputs in 24-hour mode.

Answer 7

C#, 129 125 bytes

using System;using System.Threading;class P{static void Main(){for(;;){Console.WriteLine(DateTime.Now);Thread.Sleep(1000);}}}

Ungolfed:

using System;
using System.Threading;

class Program
{
    static void Main()
    {
        for (;;)
        {
            Console.WriteLine(DateTime.Now);
            Thread.Sleep(1000);
        }
    }
}

Answer 8

PHP, 24 bytes

for(;;)echo date("\rr");

\r clears the current line before printing the date/time using the r flag. Therefor it doesn't have to wait or delay the output for a second. Also the cursor is always positioned behind the output, which would be different for r\r where it would overlay the first character of the output.

Answer 9

AppleScript, 112 93 45 bytes

repeat
delay 1
log(do shell script"date")
end

This repeats in a loop, does the bash script date, gets its returned string, and outputs it to the Messages pane. Why I didn't do this at first, I'll never know.

Using Node:

Let's have a odd useless combination, shall we?

This was inspired by my Vitsy answer, which also uses JS to get the date.

tell app"System Events"
tell app"Terminal"to activate
keystroke"node
"
repeat
delay 1
keystroke"Date()
"
end
end

What I do here is I tell the System Events application to get terminal as the front window, then enter node with the terminal by telling System Events to simulate keystrokes of n, o, d, e, followed by a newline. It then enters a loop in which it delays for a second, tells node to do Date() by the same method, then going back to the top of the loop.

This answer is mostly to demonstrate the odd things that Applescript allows you to do.

Answer 10

Unix Shell + procps, 12 bytes

procps is a package providing CLI utils for browsing procfs, a virtual filesystem generated by the kernel to provide information about processes.

The watch command reruns a command every on an interval, that defaults to 2. Set it to 1, and run ., and voilá, watch suppresses stderr.

watch -n1 .

The time is in the upper right.

---

incidentally, watch is very handy for spying on the progress of a lengthy dd or cp.

Answer 11

Factor, 43 bytes

[ [ t ] [ now "%c" strftime print ] while ]

An anoymous function. Use it like ~quotation~ call.

Answer 12

Pylongolf, 11 bytes

>}~.1000w.<

}~ pushes the current time into the stack and then prints it.
. the dots reset the stack.
1000w pushes 1000 into the stack and then waits that time.

Answer 13

Jelly, 8 bytes

7ŒTṄœS1ß

Try it online!

How it works

7ŒTṄœS1ß  Main link. No arguments.

7         Yield 7 (or 111 in binary).
 ŒT       Time; return hours, minutes and seconds (lower three bits).
   Ṅ      Print, followed by a linefeed.
      1   Yield 1.
    œS    Sleep for 1 second, return the time.
       ß  Call the main link recursively.

Answer 14

Python, 53 bytes

This one prints the date and year as well as the time, so I don't know if it's allowed.

import time
while 1:print(time.ctime());time.sleep(1)

EDIT: J.F.Sebastian made a shorter one.

Answer 15

Scratch, 15 bytes

(scoring used)
This script is essentially what it says. It joins the hour value, then a colon, then the minute value, then a colon, then the second value. The downside is that Scratch reads 01 as 1, so it might not be valid without making the script longer.

Answer 16

Lua, 51 Bytes

Since the previous owner of this answer in 56 Bytes doesn't update anymore when suggested improvments, here's a 51 Bytes solution heavily based on his:

v=1::a::v=os.date'%c'l=v~=l and print(v)or v goto a

Answer 17

C#, 102 bytes

using System;class P{static void Main(){for(var s="";;)if(s!=(s=DateTime.Now+"\n"))Console.Write(s);}}

An infinite loop that prints whenever the time changes. Default precision for C# date printing is to the second, so that works out nicely.

Answer 18

Nim, 55 54 bytes

import os,times
while on:echo getClockStr();sleep 1000

on is an alias for true. Prints the result of the times module's getClockStr proc, which formats the time nicely in 24-hour format, then uses the os module's sleep proc to sleep a second.

Answer 19

Tellurium, 8 bytes

[i|t^¨]

The code that is after the | and before the ] is run forever (i).

It changes the value of the current cell to the current time (t), outputs the current cell's value using ^, and waits for 1 second (¨) before continuing.

Answer 20

Mathematica, 27 21 bytes

With 2 bytes saved thanks to Xavier.

Dynamic@{Now,Clock[]}

Answer 21

Clojure, 140 bytes

(loop[l 0](let[c(System/nanoTime)](recur(if(>=(- c l)1e3)(do(println(.format(java.text.SimpleDateFormat."h:m:s a")(java.util.Date.)))c)l))))

Full program. Loops continually; keeping track of the last time it printed. If 1000ms have passed, it prints, then resets the time.

Java interop really bloats this up, but not much can be done about that.

Ungolfed:

(defn current-time []
  (loop [last-ns 0]
    (let [current-time (System/nanoTime)]
      (recur
        (if (>= (- current-time last-ns) 1e3)
          (do
            (println (.format (java.text.SimpleDateFormat. "h:m:s a") (java.util.Date.)))
            current-time)
          last-ns)))))

Using sleep (which seems to be of questionable validity), 100 bytes

(while[](Thread/sleep 1e3)(println(.format(java.text.SimpleDateFormat."h:m:s a")(java.util.Date.))))

Ungolfed:

(defn current-time []
  (while []
    (Thread/sleep 1e3)
    (println (.format (java.text.SimpleDateFormat. "h:m:s a") (java.util.Date.)))))

Answer 22

Fourier, 46 20 bytes

This is a fairly simple program which loops infinitely, using the newly added date functions, delay function and clear screen function.

This does not show a leading zero on the minutes or the seconds value when either are less than ten.

(@2do58a1do58a0do1;)

Try it online!

_{Note: this program will not work on http://fourier.tryitonline.net due to differences in the way interpreters work.}

Answer 23

QBIC, 6 bytes (nc)

{_C?_d

QBIC is newer than this challenge. In fact, this challenge is the reason QBIC has a _C command (for CLS - Clear the screen) and the _d/_D commands (for TIME$ and DATE$ resp).

Explanation

{        Start infinite loop
 _C      Clear screen
   ?     PRINT
    _d   TIME$ (which holds the system's time in QBasic)

Answer 24

MOO, 46 bytes

while(!suspend(!player:tell(ctime())))endwhile

Sleeps for one second between outputs, regardless of execution time (and it's impossible to know sub-second timings anyway

Answer 25

Factor, 29 bytes

[ now hh:mm:ss nl ] 1e9 every

Normally you'd give every a duration for more readability: [ ... ] 1 seconds every but if you just give it a number, it'll interpret it as nanoseconds.

Answer 26

tcl, 67

while 1 {puts [clock format [clock seconds] -format %T];after 1000}

can be tested on: http://tpcg.io/_MQDV24

Answer 27

PHP, 36 34 bytes

a:echo'
'.date(r);sleep(1);goto a;

The line break can be \n but it's nicer to convert the script to the old Macintosh line format and make it \r, then the time is neatly updated on the same line.

Updates:

1. Removed short open tag as per this meta answer

Answer 28

05AB1E, 13 bytes

[žažbžc)':ý,w

Should work, but I don't have Python 3, so I can't test.

Answer 29

Elixir, 95 bytes

def f, do: 1000|>Stream.interval|>Enum.each(&(&1&&DateTime.utc_now|>DateTime.to_time|>IO.puts))

Answer 30

*><>, 16 bytes

'::'hnomnosnaoaS

000webhostapp interpreter.

Note: it sometimes skips a second (e.g. 12:34:6 → 12:34:8), because you can't wait exactly a second with total accuracy. Unfortunately there isn't any way to fix this.