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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body{text-align:left!important}#answer-list,#language-list{padding:10px;float:left}table thead{font-weight:700}table td{padding:5px}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <link rel="stylesheet" type="text/css" href="//cdn.sstatic.net/codegolf/all.css?v=83c949450c8b"> <div id="answer-list"> <h2>Leaderboard</h2> <table class="answer-list"> <thead> <tr><td></td><td>Author</td><td>Language</td><td>Size</td></tr></thead> <tbody id="answers"> </tbody> </table> </div><div id="language-list"> <h2>Winners by Language</h2> <table class="language-list"> <thead> <tr><td>Language</td><td>User</td><td>Score</td></tr></thead> <tbody id="languages"> </tbody> </table> </div><table style="display: none"> <tbody id="answer-template"> <tr><td>{{PLACE}}</td><td>{{NAME}}</td><td>{{LANGUAGE}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table> <table style="display: none"> <tbody id="language-template"> <tr><td>{{LANGUAGE}}</td><td>{{NAME}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table>

Answer 1

Japt, 8 bytes

Japt is a shortened version of JavaScript.

1e3i@OpÐ

Test it online!

How it works

1e3i@       // Repeat this function every 1e3 milliseconds:
     OpÐ    //  Output new Date(), followed by a newline.

Note that this also outputs a seemingly random integer when the code is run. To get rid of this, use this code:

1e3i@OpÐ};P

On my computer, the time is formatted as 2015-11-28T16:00:18.013Z. If you don't like that, try this code instead:

1e3i@OpÐ s8};P

Which will lovingly print your time in the format 11:00:18 AM.

Answer 2

K, 25 24 Bytes

Removed semicolon from the end of the func!

      .z.ts:{-1@$18h$x}
      \t 1000
  13:11:44
  13:11:45
  13:11:46
  13:11:47
  13:11:48
  ...


.z.ts is called every 1000 milliseconds. 
x is the time. 
18$x casts the time to the appropriate format. 
$ - strings the result. 
-1@(stringed result) - prints the string to the console.

*Edit Below is less but I wasn't sure whether the time format was allowed;

    .z.ts:{-1($x)}
    \t 1000
2016.08.01D00:35:37.392683000

Answer 3

Pure bash, 116 113 96 bytes

Using bash version >= 5.0, there is a new EPOCHREALTIME variable:

for((;;)){
IFS=. read s m<<<$EPOCHREALTIME
printf '%(%c)T\n'
sleep .$[(3000000-10#$m)%1000000]
}

This will output something like:

mar 03 jan 2023 10:28:27
mar 03 jan 2023 10:28:28
mar 03 jan 2023 10:28:29
...

Note: In order to save 3 byte, I've done something to not do: mixing time() (printf '%()T') and gettimeofday() ($EPOCHREALTIME). See: WARNING! About mixing $EPOCHSECONDS and $EPOCHREALTIME (better line 3 would be: printf '%(%c)T.%s\n' $s)!!

With a little more precision:

for((;;)){
IFS=. read s m<<<$EPOCHREALTIME
printf '%(%c)T.%s\n' $s $m
read -rn1 -t .$[(3000000-10#$m)%1000000] _
}

Will output something like:

mar 03 jan 2023 10:52:44.183297
mar 03 jan 2023 10:52:45.000324
mar 03 jan 2023 10:52:46.000424
mar 03 jan 2023 10:52:47.000300
mar 03 jan 2023 10:52:48.000341
...

Answer 4

C/C++, 219 Bytes

Here is a first pass attempt. It is written in C++ but uses only C functionalities, so it could be used as C code with only changes to the include statements (I think).

#include<stdio.h>
#include<ctime>
time_t r;struct tm*x;int main(){char c[9],b[9];time(&r);x=localtime(&r);strftime(c,9,"%T",x);puts(c);for(;;){time(&r);x=localtime(&r);strftime(b,9,"%T",x);if(b[7]!=c[7]){break;} }main();}

I think everything is pretty straightforward. It takes the time at the beginning of the main function, then it continues getting time until one second has passed. It then calls itself.

Ungolfed:

#include<stdio.h>
#include<ctime>
time_t r;struct tm*x;
int main(){
    char c[9];char b[9];
    time(&r);
    x=localtime(&r);
    strftime(c,9,"%T",x);
    puts(c);
    for(;;){
        time(&r);
        x=localtime(&r);
        strftime(b,9,"%T",x);
        if(b[7]!=c[7]){break;} // break when the 'second' changes
    }
    main();
}

Answer 5

Vimscript, 44 bytes

while 1
echo strftime("%T")
sleep 1
endwhile

Run like so:

vim -c ":so FILE"

Answer 6

Pyth, 19 16 bytes

It takes the relevant part of the datetime list and joins by colons. Then it passes till the second changes, with the entire thang wrapped in an infinite loop.

#j\:KP.d2WqeK.d8

While it obviously doesn't work online, you can check its main idea here.

Answer 7

PHP, 33 bytes

<?for(;;)sleep(print date("r
"));

Output is similar to Sat, 28 Nov 2015 11:25:16 +0700, i.e. RFC 2822.

Answer 8

Mathematica, 41 36 bytes

While[1>0,Echo@DateString[];Pause@1]

Works as a script.

Answer 9

CJam, 21 bytes

L{et6<':*_@={_oNo}|}h

Try it online! Note that the online interpreter will kill the program after one minute.

Same idea, but with pretty output:

L{et6<3>"%02d:"fe%sW<_@={_oNo}|}h

Try it online!

Answer 10

Go, 64 69 79 bytes

Go isn't very golfy.

package main;import(."fmt";."time");func main(){for{Println(Now());Sleep(1e9)}}

You could try it here or on another online interpreter however, for{} is an infinite loop and those are disallowed for obvious reasons. I haven't actually tested this^{there are no go interpreters for my android ):} but it should work in theory.

Running it locally might cause your CPU fan to speed up, but it won't hog memory. If it crashes with some sort of OOM-error or panic: runtime out of bound, just change it to for x:=0;x<9999;x++{ ... }.

Answer 11

SpecBAS - 45 bytes

Prints in the upper left corner for a continuously updating 24 hour clock. Pressing Esc stops it running.

1 TEXT AT 0,0;TIME$(TIME,"hh:mm:ss"): GO TO 1

Answer 12

Processing, 68 bytes

void draw(){frameRate(1);println(hour()+":"+minute()+":"+second());}

Easy one I have to admit. In processing there is the draw() method which is called at a specific frequency that can be modified during the execution.

Answer 13

Ruby, 25 24 bytes

Thanks @manatwork for golfing off a byte :P

loop{puts`date;sleep 1`}

Not bad.

Answer 14

Ceylon, 126 112 bytes

import ceylon.time{now}void p(){for(e in{now().time().string[0:8]}.cycled.paired){if(e[0]!=e[1]){print(e[1]);}}}

This uses the ceylon.time library for getting the current time (in the default timezone) and formatting it (the .string function for time outputs something like 22:33:45.234, so I just take the first 8 characters of it).

Unfortunately, there seems to be no sleep function in Ceylon (because it is not easy to implement in JavaScript), therefore I'm doing a busy loop here, comparing each formatted string to the previous one and printing only when there is a change.

Here is a formatted version of the second version, which uses a for-loop over an infinite iterable:

// print the current time (each second).
//
// Question:  http://codegolf.stackexchange.com/q/65020/2338
// My answer: http://codegolf.stackexchange.com/a/65130/2338

import ceylon.time {
    now
}

void p() {
    for(e in { now().time().string[0:8] }.cycled.paired) {
        if(e[0]!=e[1]) {
            print(e[1]);
        }
    }
}

Using a < instead of != would save a character, but then the program would stop working as soon as the clock hits midnight.

This was the original, more functional, version resulting in 112 characters:

import ceylon.time {
    now
}

void p() {
    { now().time().string[0:8] }
        .cycled
        .paired
        .map((e) => e[0] != e[1] then e[1])
        .coalesced
        .each(print);
}

Answer 15

Hassium, 43 Bytes

func main(){print(time())sleep(1000)main()}

See expanded here

Answer 16

sh (+ top), 7 bytes

Script (Debian8):

top -d1

Script (NetBSD7):

top -s1

(both without trailing newline)

Output (1st line only, Debian8):

top - 16:25:15 up 3 days,  8:56,  4 users,  load average: 0,97, 1,10, 1,03

Output (1st line only, NetBSD7, different time zone):

load averages:  1.46,  1.28,  1.22; (SPACES) up 44+08:52:28 (SPACES) 15:22:06

The amount of spaces depends on the terminal width.

Answer 17

C, 74 73 bytes

#include<time.h>
main(){for(time_t t;!sleep(1);time(&t))puts(ctime(&t));}

The code can work even without #include <stdio.h> and #include <unistd.h>, see live code example on ideone.com -- note: the sleep is zero there, to generate some output before the time limit has been exceeded.

The first output line should be ignored ("Extra output doesn't really matter, as long as the program at some point continuously outputs time.").

Answer 18

PureBasic, 64 59 bytes

Not much to say, infinite loop, output time to the debug window with a 1000 millisecond delay

a:
Debug FormatDate("%hh:%ii:%ss",Date())
Delay(1e3)
Goto a

Answer 19

Prolog (SWI), 72 bytes

Formating to user_output stops working when using sleep, so I had to save the time to a variable and print it explicitly.

Code:

p:-repeat,get_time(T),format_time(atom(X),'%T',T),write(X),sleep(1),1=0.

Explained:

p:-repeat,                      % loop until success
   get_time(T),                 % Get current timestamp
   format_time(atom(X),'%T',T), % Format timestamp as HH:mm:ss
   write(X),                    % Print time
   sleep(1),                    % Sleep 1 second
   1=0.                         % Fail and go back to repeat

Answer 20

Vitsy + bash, 13 11 bytes

_{This language feature was made after this question, but not for this question.}

<w1Z,'date'
<           Loop leftwards in the code.
            Rest of code is written in reverse for "readability". 
 'etad'     Push 'date' to the stack.
       ,    Do the shell script for what's in the stack.
        Z   Output the result.
         1w Wait a second.

Or, using eval...

<w1Zn"Date()"
<             Go leftwards through this code in order to loop infinitely. 

              Rest of code is written in reverse for "readability". 

 ")(etaD"     Push "Date()" to the stack.
         n    Eval through JS.
          Z   Output everything.
           1w Delay for one second.

Try it online!

Answer 21

Mouse-2002, 84 bytes

Mouse is cool, but it's not the golfiest stack based language on the planet (well, not until I update it in a reimplementation -- then it will be better.)

0&FIX 2&WIDTH "!"(&HOUR &!DEC ":"&MIN &!DEC ":"&SEC &!DEC 8!'8!'8!'8!'8!'8!'8!'8!')$

The 8!' prints the character with ASCII code 8, or backspace. You probably need an ANSI terminal to run this; it updates in place by backspacing over itself and writing the new time once per second.

sample use:

$ mouse clock2.mou

19:47:34

Based on this, but golfed.

Answer 22

Python 2, 85 bytes

import time;while 1:print __import__('datetime').datetime.now().time();time.sleep(1)

import time;time.sleep() has 2 fewer bytes than __import__('time').sleep(), while import datetime;datetime.datetime.now() has 2 more bytes than __import__('datetime').datetime.now().

Answer 23

Emacs Lisp, 83 bytes

(run-with-timer 1 1(lambda()(message(format-time-string"%H:%M:%S"(current-time)))))

Answer 24

Groovy, 40 37 bytes

Not very golfable :(, thanks to FlagAsSpam for for(;;) :)

for(;;){print(new Date());sleep 1000}

Answer 25

bash, 35 bytes

Just for kicks

yes|mapfile -tc1 -C'date;sleep 1 #'

Also 35,

x='x[`date>&2;sleep 1`${!x}]'<${!x}

I think it's unlikely there's anything shorter than exec $0.

Answer 26

Python 3, 48 bytes

from time import*
while[sleep(1)]:print(ctime())

It is a @Mego's Python 2 solution tweaked to work on Python 3.
Here's Jupyter notebook to see the results and try it.

Answer 27

Lua, 56 bytes

Lua is pretty hard to golf...

v=1
while 1 do v=os.date'%c' l=v~=l and print(v)or v end

There are few online interpreters that allow infinite loops; one of the few I've found is this one. This repeatedly converts the current system time to a date-time string and outputs that string when it's different from the last.

Ungolfed:

current = 1
while 1 do 
    current = os.date('%c') 
    last = current ~= last and print(current) or current
end

Answer 28

Matlab, 50 42 bytes

while 1;pause(1);disp(datestr(now,13));end

Answer 29

Perl 6, 34 30 bytes

Perl 6 is looooong, but I like it. Yes, all the whitespace is needed.

sleep 1 while say DateTime.now

Hooray for postfix syntax!

Answer 30

F#, 101 98 bytes

open System;while 1=1 do(DateTime.Now.ToString"HH:MM:ss"|>printfn"%s";Threading.Thread.Sleep 1000)

Pretty straightforward: print the current time in the correct format, wait a second, then repeat. Forever.

Credit to @VoteToClose and @RikerW for the help.