Hello

I am running Linux with kernel 6.6.47 and am running emacs in xterm, using the -nw command line argument.

I am new to emacs and was experimenting with the suspend-emacs command. Following the example on https://www.gnu.org/software/emacs/manual/html_node/elisp/Suspending-Emacs.html.

When following the example, I added the suspend-resume-hook to my .emacs.d/init.el file. When I run M-: (suspend-emacs "pwd") it does not show the current working directory. But when I do fg from the terminal that I got into, I see the "Resumed!" message.

I asked in the libera chat about that, and also in the gnu-help-emacs list. I have been talking to wasamasa on libera chat (#emacs-beginners) and we pinpointed the problem to the stuff_char function (in https://git.savannah.gnu.org/cgit/emacs.git/tree/src/sysdep.c#n403). We came to this point from stuff_buffered_input (https://git.savannah.gnu.org/cgit/emacs.git/tree/src/keyboard.c#n11963), and from  suspend-emacs function definition (in https://git.savannah.gnu.org/cgit/emacs.git/tree/src/keyboard.c#n11908).

The stuff_char function is using ioctl with TIOCSTI. TIOCSTI requires CAP_SYS_ADMIN capability. You can set this capability using sysctl setting dev.tty.legacy_tiocsti to 1.

Unless I had set "dev.tty.legacy_tiocsti" to 1 I could not run the suspend-emacs command with an argument string.

Either emacs can check the return value of ioctl in stuff_char and if there return value is EPERM, then handle this accordingly, with a message regarding the problem.

Or the information relating to the kernel version and CAP_SYS_ADMIN can be added to the infor page os suspend_emacs, along with the information on how to set this capability using sysctl.

Kind Regards

Riza Dindir