Getting pid and details for topmost window

Question

Does anyone know how to get the PID of the top active window and then how to get the properties of the window using the PID? I mean properties like process name, program nam

Answer 1

Am very very late to the party, but I had a similar problem, and I think this can help someone else who has the same problem. There is a command line trick to do this, you can try execvp'ing it, or executing it redirecting the output to your code

xprop -id $(xprop -root _NET_ACTIVE_WINDOW | cut -d ' ' -f 5) _NET_WM_NAME WM_CLASS

gives the window name, as well as the program name. Eg, for this tab, it gives me

_NET_WM_NAME(UTF8_STRING) = "linux - Getting pid and details for topmost window - Stack Overflow - Mozilla Firefox"

WM_CLASS(STRING) = "Navigator", "Firefox"

Answer 2

Extracted the gist of xprop into https://github.com/mondalaci/current-window-linux

Works but sometimes segfaults - needs to be fixed and cleaned up.

Answer 3

there is a command in linux call xprop which is a utility for displaying window properties in an X server. In linux xprop -root gives you the root windows properties and also other active programs. then you can get the ID of the active window using this command:

xprop -root | grep _NET_ACTIVE_WINDOW\(WINDOW\)

to get just the active window ID ( without "_NET_ACTIVE_WINDOW(WINDOW): window id # " in the beginning of the line ) use this command:

xprop -root | awk '/_NET_ACTIVE_WINDOW\(WINDOW\)/{print $NF}'

now you can save this command output in a user defined variable:

myid=xprop -root | awk '/_NET_ACTIVE_WINDOW\(WINDOW\)/{print $NF}'

xprop have an attribute call -id. This argument allows the user to select window id on the command line. We should look for _NET_WM_PID(CARDINAL) in output ... so we use this command:

xprop -id $myid | awk '/_NET_WM_PID\(CARDINAL\)/{print $NF}'

this gives you the topmost active window process ID.

to be more trickey and do all things in just 1 command ... :

 xprop -id $(xprop -root | awk '/_NET_ACTIVE_WINDOW\(WINDOW\)/{print $NF}') | awk '/_NET_WM_PID\(CARDINAL\)/{print $NF}'

Now I can run these commands via my C++ program ( in linux ) using popen function, grab stdout and print or save it. popen creates a pipe so we can read the output of the program we are invoking.

( you can also use '/proc' file system and get more detail of a PID ('/proc/YOUR_PID/status') )

#include <string>
#include <iostream>
#include <stdio.h>
using namespace std;

inline std::string exec(char* cmd) {
    FILE* pipe = popen(cmd, "r");
    if (!pipe) return "ERROR";
    char buffer[128];
    std::string result = "";
    while(!feof(pipe)) {
        if(fgets(buffer, 128, pipe) != NULL)
                result += buffer;
    }
    pclose(pipe);
    return result;
}

int main()
{
    //we uses \\ instead of \ ( \ is a escape character ) in this string
 cout << exec("xprop -id $(xprop -root | awk '/_NET_ACTIVE_WINDOW\\(WINDOW\\)/{print $NF}') | awk '/_NET_WM_PID\\(CARDINAL\\)/{print $NF}'").c_str(); 
 return 0;
}

Answer 4

The PID of a window owner is stored in the X property _NET_WM_PID. Note that this is only a de-facto standard.

You have to find the id of the window first, then you can query for the property. I don't know of any abstraction QT provides for this, so you will probably have to use xlib or xcb.

Play with the tool xprop for starters.

Answer 5

I run this command on a terminal:

sleep 5s; ps -Flwwp $(xdotool getwindowpid $(xdotool getwindowfocus))

Run it, change the focus to the relevant window, wait 5 seconds, then back to terminal. Voilà!

Answer 6

Install wmctrl (from the repositories). wmctrl -lp could be what you want. You can always take a look at the source if you need it from your program.