[SOLVED] A program to send a character to another tty fails in 64-bit

I wrote a small program to send a character to a terminal other than my own. I moved to 64-bit recently and the program fails.

I open a terminal with:

	hTTY = open(/dev/tty3, O_WRONLY|O_NONBLOCK);

then send a character with:

 result=ioctl(hTTY, TIOCSTI, argv[2]);

The open succeeds but the ioctl fails with errno=1, Operation not permitted.

If I send to its own tty it works. Ownership and permissions of the target terminal don't matter. If I do it as root it works.
What's the difference between 32 and 64 bit?

Most likely you are hitting capabilities. My guess would be you need CAP_SYS_TTYCONFIG.

http://man7.org/linux/man-pages/man7...ilities.7.html

Originally Posted by smallpond Most likely you are hitting capabilities. My guess would be you need CAP_SYS_TTYCONFIG.

Thanks. I didn't know about this; BTW it's CAP_SYS_TTY_CONFIG. I wrote the program a few years ago. I worked until I switched to 64-bit, same kernel version.

You updated system to 64 bits keeping same group settings for user?

Originally Posted by keefaz You updated system to 64 bits keeping same group settings for user?

Yes.

Setting the sticky bit makes it work.