Add process devices

[vinc]

Add process device files to change process data from userspace:

• /dev/proc/id to get the PID
• /dev/proc/dir to get or set the current dir
• /dev/proc/env to get or set env vars
• /dev/proc/user to get the current user

[vinc]

We can't use print to change the current dir in the shell as it's an external program, but an echo builtin will do:

~
> echo /tmp => /dev/proc/dir

/tmp
> echo $dir
/tmp

The variable to get the current dir in the shell changed from $DIR to $dir as it is a shell variable and not an environmental variable.

[vinc]

I removed env and replaced it by a new option --env for the shell builtin set:

> read /dev/proc/env
HOME = "/usr/vinc"
USER = "vinc"

> echo TEST=42 => /dev/proc/env

> read /dev/proc/env
HOME = "/usr/vinc"
TEST = "42"
USER = "vinc"

> date
2026-04-21 19:44:24 +0000

> set --env TZ 7200

> read /dev/proc/env
HOME = "/usr/vinc"
TEST = "42"
TZ   = "7200"
USER = "vinc"

> date
2026-04-21 21:44:43 +0200

[vinc]

TODO:

• How to unset an env var?
• How to login from userspace?
• How to keep $dir up to date in the shell?
• Replace print program with a shell builtin?