mjhjmtu

Please,

can someone shed some light for me on .xinitrc file? I struggle to find a good manual to answer a couple of my practical questions:

• It declared itself as general Bash script but in fact it is not.


• Why some command require exec and some not?


• What is this exec command anyway?


• Is it a binary or a syntactic construct specific to xinitrc?


• What can be run by exec and what not?


• How to set environmental variables correctly?

Most users of mainstream distros does not have to even know about xinitrc, and same was true for me, until I had to setup Kodi "makeshift" shell; using super minimalist window manager TWM and launching Kodi full screen, because kodi-standalone shell does not work for me.

But back to the xinitrc:

Working example:

#!/bin/bash
/usr/bin/twm &
sleep 1
exec xterm

Why twm and sleep do not need exec but xterm does?

Not working example:

#!/bin/bash
/usr/bin/twm &
sleep 1
exec WINDOWING=x11 /usr/bin/kodi -geometry +0+0

Here exec executed only WINDOWING=x11 but ignored the rest of the line. I made it working only by wrapping WINDOWING=x11 /usr/bin/kodi -geometry +0+0 into another Bash script, this time an ordinary one, and that one put as the only argument to exec; then it finally worked.

The exec command replaces the current shell process with the process resulting from executing the given command. Without exec, control would be handed back to the waiting shell session once the command terminates. With exec, the current shell is replaced, so no further commands would be run from your script from that point on.

The ~/.xinitrc file is a shell script. It starts the window manager (twm in your case), and possibly other X11 clients that you may want to start initially (like xterm or some other terminal, and xeyes, obviously). There is no special syntax for this script apart from that it should be a valid script (since it's run by a shell script interpreter).

In your first example, you use

exec xterm

This replaces the current shell process with xterm. Without exec, you would have the exact same visible effect, but the .xinitrc script would hang around in the background waiting for xterm to terminate before itself terminating (since that was the last command in the file).

Note that if you had done exec twm, the shell would have replaced itself with twm which means that it would not be able to run the other commands in the script. This is why you instead start twm as a background process (with & at the end). The sleep is there to allow twm to start up properly before starting the terminal. I don't think this is strictly necessary. In fact, if you don't need window decorations or to be able to move windows around or resize them, there is no need to even run twm or any other window manager (at least not for running a full screen xterm).

In your second example, you use

exec WINDOWING=x11 /usr/bin/kodi -geometry +0+0

Now, the exec command can't be used to set environment variables like that. Instead, you would set and export the WINDOWING variable before invoking kodi:

export WINDOWING=x11
exec /usr/bin/kodi -geometry +0+0