How do I find the windowid to pass to screencapture -l?

Question

The command line utility screencapture claims to be able to capture a single window without requiring interaction, but I can't figure out what to pass it.

-l<windowid> capture this windowsid

It's not the process id of the the application.

score 30 · Accepted Answer · edited Apr 13 '17 at 12:45

30

For some applications you can use AppleScript:

screencapture -l$(osascript -e 'tell app "Safari" to id of window 1') test.png

It doesn't work with Chrome though.

The IDs are also shown in Quartz Debug (available from developer.apple.com/downloads) if you run defaults write com.apple.QuartzDebug QuartzDebugPrivateInterface -bool true.

edited Apr 13 '17 at 12:45

Community

1

answered Jul 16 '12 at 18:49

Lri

105,117

1

Unfortunately, this doesn't work with non-Applescriptable apps like Eclipse or Google Chrome. – Cajunluke Jul 16 '12 at 18:52
1

Yeah, my target app is not Applescriptable :( But thank you anyway. – Gareth Simpson Jul 16 '12 at 19:13
2

Note that window ids are not guaranteed to correspond to the Quartz window id even in applications that are scriptable. – Chris Page Aug 11 '12 at 05:23
Quartz debug seems to no longer exist or else it has been renamed or bundled? – gman May 31 '18 at 03:37
1

Quartz Debug is included in "Additional Tools for Xcode" available at https://developer.apple.com/download/more/. – Nicholas Riley Nov 23 '19 at 15:53

score 14 · Answer 2 · answered Jun 02 '13 at 18:21

14

I wrote a little command line utility to retrieve the Window ID for apps that don't support AppleScript. Get it here: https://github.com/smokris/GetWindowID

You can then capture a specific window by specifying its bundle name and window title:

screencapture -l$(./GetWindowID "Vuo Editor" "untitled composition") VuoEditorWindow.png

answered Jun 02 '13 at 18:21

smokris

684

Hi, I'm trying to use it but I'm not sure on what I'm doing. I've downloaded the Makefile,GetWindowID.m. But when I launch the command ./GetWindowID.m it gives me this error:./GetWindowID.m: line 4: syntax error near unexpected token (' ./GetWindowID.m: line 4:int main(int argc, char **argv)' – KingBOB Sep 06 '13 at 22:25
1

@Giorgio: Open a Terminal window and change to the folder that contains Makefile and GetWindowID.m, then run the command make. It will produce a binary called GetWindowID, which you can then invoke using the command I described in my answer. – smokris Sep 24 '13 at 04:37

thismachine · Answer 3 · 2020-10-01T19:42:26.650

7

I wrote a command line utility that wraps over screencapture and the Quartz windowing library.

Grab it here: https://github.com/alexdelorenzo/screenshot

Use it like this:

screenshot Chrome -t "Stack Overflow"

edited Oct 01 '20 at 19:42

answered Mar 22 '15 at 16:10

thismachine

81

Have you missed double-quote? – kenorb Aug 17 '15 at 08:36

score 4 · Answer 4 · answered Jun 18 '22 at 13:58

4

As far as I can tell, there still isn't an easy way to get the window ID from the command line. However today (in 2022) we have Shortcuts that allow you to easily take a screenshot of a single window

Open the Shortcuts app
Create a new shortcut
Use the "Find Windows" action, and filter until you get the window you want
Use the "Save File" action and save the file (it seems to be a bit weird, you choose a folder to save to (in my case reinoud), and then in subpath you put the file name). Just make sure that you set the first variable in this action (which is Window by default) to be "Image", by clicking on "Window" and select "Image" from the "Get" box.
Save the Shortcut by giving it a name
If you want to run the shortcut from the commandline, just use shortcuts run "Find My to File" (if Find My to File is the name of the shortcut)

answered Jun 18 '22 at 13:58

Claude

236

thanks @claude for this, works perfectly! I feel you had a similar idea to what I've just been trying to do? ... https://twitter.com/find_my_brolly – ChrisB Jun 19 '22 at 15:28
Haha nice! I tried to make my position in a marathon known to my iPhone-less family. Didn’t quite work, seems that the “find my” screen doesn’t update that often when the machine is on screensaver….. – Claude Jun 19 '22 at 15:32
I like this solution, since I could add "Cropped Image" action as I need – flyisland Aug 30 '22 at 12:31

score 2 · Answer 5 · answered Jan 14 '22 at 11:32

The window ID does not seem to be generally exposed to AppleScript. However, the window geometries are exposed. So instead of using screencapture -l you can use screencapture -R x,y,w,h to capture the specific portion of the display covered by the target window. With AppleScript, the process can be selected by Unix PID as property "unix id".

Assuming the process has just one window and your PID is in $PID:

screencapture -R \
`osascript -e 'tell application "System Events" to get { position, size } of first window of (first process whose unix id is '$PID')' | tr -d ' '` \
window.png

If the process has multiple windows, you need to select by the target window title:

screencapture -R \
`osascript -e 'tell application "System Events" to get { position, size } of (first window whose title is "My window titlebar text") of (first process whose unix id is '$PID')' | tr -d ' '` \
window.png

Tip: You can list the selectable properties of any object with get properties: osascript -e 'tell application "System Events" to get properties of first process whose unix id is '$PID

How do I find the windowid to pass to screencapture -l?

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