CODEWITHSUNDEEP
clinuxinputmouse
thundertrick
thundertrick

Reputation: 1674

How can I control mouse movement in Linux?

I try to control the mouse in Linux. Xlib seems to work, but when I try to use it with OpenCV, it keeps returning:

Resource temporarily unavailable

So I decided to write "/dev/psaux". The code is as follows:

#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


int main() {
    unsigned char a[5] = {0, 0xff, 0, 0x28, 0xff};
    int fp = open ("/dev/psaux", O_WRONLY);
    if(!fp)
        printf("open error:%s\n", strerror(errno));

    for(int i = 0; i < 10; i++)
        printf("write:%d\t\t%s\n", write(fp, a, 5), strerror(errno));
    close(fp);
    return 0;
}

Compile it with:

gcc  my_psaux.c -o my_psaux -std=gnu99 -g

Run

sudo ./my_psaux

and get

write:5    Success
write:5    Success
write:5    Success
write:5    Success
write:5    Success
write:5    Success
write:5    Success
write:5    Success
write:5    Success
write:5    Success

However, the mouse doesn't move. Then I open a new terminal, type in "sudo cat /dev/psaux" and run "my_psaux". But I just cat nothing. Nothing is written into "/dev/psaux"

How can I fix this?

If this is not a good method to control the mouse, is there another one?

Upvotes: 17

Views: 19752

Answers (2)

R.. GitHub STOP HELPING ICE
R.. GitHub STOP HELPING ICE

Reputation: 215447

The mouse is not a loopback/echo device. It's more like a terminal. Would you expect writing data to a terminal (which would appear on the screen) to make the same characters come back to you as input? The same applies to the mouse; the only point in writing to it is to send escape sequences that change its mode (e.g. the protocol used or the resolution).

If you want to "control" the mouse, you have to inject events some other way, or provide a fifo (named pipe) or pseudo-tty in place of /dev/psaux for the input system to read from. However this is probably a rather misguided way to do things...

If you explain why you need to control the mouse, perhaps we could offer you better alternative approaches to what you're trying to do.

Upvotes: 2

thundertrick
thundertrick

Reputation: 1674

Great thanks to R... for reminding me of some other ways instead of /dev/psaux

I tried /dev/input/mouse* and /dev/input/event*

By using

cat /proc/bus/input/devices

I get this:

I: Bus=0003 Vendor=0461 Product=4d81 Version=0111
N: Name="USB Optical Mouse"
P: Phys=usb-0000:00:1d.0-1/input0
S: Sysfs=/devices/pci0000:00/0000:00:1d.0/usb6/6-1/6-1:1.0/input/input10
U: Uniq=
H: Handlers=mouse2 event10
B: EV=17
B: KEY=70000 0 0 0 0 0 0 0 0
B: REL=143
B: MSC=10

After testing, only /dev/input/event10 works. The code is as follows:

#include <stdio.h>
#include <unistd.h>
#include <linux/input.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>

int main() {
  struct input_event event, event_end;

  int fd = open("/dev/input/event10", O_RDWR);
  if (fd < 0) {
    printf("Errro open mouse:%s\n", strerror(errno));
    return -1;
  }
  memset(&event, 0, sizeof(event));
  memset(&event, 0, sizeof(event_end));
  gettimeofday(&event.time, NULL);
  event.type = EV_REL;
  event.code = REL_X;
  event.value = 100;
  gettimeofday(&event_end.time, NULL);
  event_end.type = EV_SYN;
  event_end.code = SYN_REPORT;
  event_end.value = 0;
  for (int i=0; i<5; i++) {
    write(fd, &event, sizeof(event)); // Move the mouse
    write(fd, &event_end, sizeof(event_end)); // Show move
    sleep(1); // Wait
  }
  close(fd);
  return 0;
}

Upvotes: 24

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