58

I'm looking for a Windows program/script/command line function that works like Linux's watch program.

watch periodically calls another program/whatever and shows the result, which is great for refreshing an output file or similar every second:

watch cat my-output.txt

or, more powerfully:

watch grep "fail" my-output.txt

I've looked for it in cygwin's library, but it doesn't seem to be present.

13 Answers 13

14

watch is available in Cygwin, in the procps package as listed here (this info can be found via the package search on the website, here). I don't think this package is installed by the default cygwin setup, but it is one I usually select on new installs in order to have the watch command available.

The location of tools in packages usually match package names in Linux distributions (the package containing watch is procps on Debian and Ubuntu too) so if the Cygwin package search function fails you, info for/from Linux distributions may offer clues.

48

Write your own. Let's say file watch.bat contains :

@ECHO OFF
:loop
  cls
  %*
  timeout /t 5 > NUL
goto loop

and call it via, for example:

watch echo test

will echo test every 5 seconds.

  • @Keilaron: Note that your edit was bad and I had to fix it.  Please be more careful. – Scott Dec 13 '17 at 19:35
  • Simple but great. Avoids installing cygwin just for that single command. Vielen Dank! – Stef Feb 12 at 5:23
28

Powershell has the "while" command. You can use it like in Linux:

while (1) {your_command; sleep 5}

Linux version:

while true; do your_command; sleep5; done

Others:

while ($true) {netstat -an | findstr 23560; sleep 5; date}

  • 4
    You can just use while (1), because 1 is truthy. – TheQuickBrownFox May 14 '16 at 12:05
  • 1
    I also found that you can use "clear" as the last statement, so it behaves more like watch. – itmuckel Nov 11 '16 at 7:51
13

A generic Windows command oneliner to accomplish this:

for /l %g in () do @( echo test & timeout /t 2 )

Replace "echo test" with the command you wish to run repeatedly.

  • nice one, simple one liner that does the trick – user230910 Sep 25 '17 at 12:58
6

I wrote this little PowerShell module to do what you were looking for. Just put it in

C:\Users\[username]\Documents\WindowsPowerShell\Modules\Watch

and run import-module watch in PowerShell.


# ---- BEGIN SCRIPT
# Author:       John Rizzo
# Created:      06/12/2014
# Last Updated: 06/12/2014
# Website:      http://www.johnrizzo.net

function Watch {
    [CmdletBinding(SupportsShouldProcess=$True,ConfirmImpact='High')]
    param (
        [Parameter(Mandatory=$False,
                   ValueFromPipeline=$True,
                   ValueFromPipelineByPropertyName=$True)]
        [int]$interval = 10,

        [Parameter(Mandatory=$True,
                   ValueFromPipeline=$True,
                   ValueFromPipelineByPropertyName=$True)]
        [string]$command
    )
    process {
        $cmd = [scriptblock]::Create($command);
        While($True) {
            cls;
            Write-Host "Command: " $command;
            $cmd.Invoke();
            sleep $interval;
        }
    }
}

Export-ModuleMember -function Watch

# --- END SCRIPT
  • 1
    Looks pretty good but I would encourage the function to be in the Verb-Noun format (e.g. Watch-Command) with an alias of Watch (Set-Alias -Name Watch -item Watch-Command). – duct_tape_coder Mar 8 at 18:24
6

This is how I would do it in PowerShell:

while(1){ netstat -an|grep 1920;start-sleep -seconds 2;clear }

The condition while(1) is equivalent to while true, looping indefinitely.

6

It's a PowerShell one liner:

while ($true) { <your command here> | Out-Host; Sleep 5; Clear }
  • I'd put Clear first. – sastanin Oct 5 '18 at 15:53
  • it depends on how long your command takes to run and then output to display.... you can change the order, but this is the general idea – ErikW Apr 30 at 15:13
3

You can also make up a delay using the PING command, for example:

@echo off
:loop
  cls
  dir c:\temp
  REM 5000mS (5 sec) delay...
  ping 1.1.1.1 -n 1 -w 5000 >NUL
goto loop
2

I had the same issue when needing to check the file size of a file actively being worked on by another process. I ended up cloning the functionality of watch on Windows. The compiled exe as well as the source is available at the site.

watch for Windows

1

I created a watch command for windows called llwatch.

The code is both on my website landenlabs.com

and also on GitHub

You may need to use x64 to watch x64 programs and x32 for the others. Not sure how picky windows is.

  • Not sure why this was downvoted... Welcome to Super User! – jpaugh Feb 2 '16 at 14:16
1

what @harrymc said except with sleep watch.bat

@ECHO OFF
:loop
  %*
  sleep 5
goto loop

./watch.bat npm run test

npm run test every 5 sec

0

PowerShell-Watch

Code Repository

-1

I was in a hurry.... I used one suggestion and changed it a little to work for me:

for /l %g in () do @( echo test & timeout /t 2 )

I changed it to:

for /l %g in () do @( test.bat & timeout /t 2 )

And I created the test.bat file with the command line. In my case, it was:

net group /domain

I found that the echo command just printed out to the screen but did not execute the command

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