Ultimate-Linux: Userspace for Linux in Pure JavaScript

81 pointsposted 13 hours ago
by radeeyate
(github.com)

24 Comments

rkeene2

8 hours ago

I did something similar with TCL, the basis was using an extension I wrote to handle the UNIX stuff [0]. It operated an On-Premises cloud environment appliance, and `init` was just a TCL script (at one point it was a statically linked binary with the init script embedded, but that turned out to be overkill)

[0] https://chiselapp.com/user/rkeene/repository/tuapi/doc/trunk...

kalterdev

11 hours ago

It’s never early to prepare for JavaScript complete takeover.

supermdguy

10 hours ago

Reading the code, I was surprised to see that cd was implemented by calling out to the os library. I assumed that was something the shell or at least userspace handled. At what level does the concept of a “current directory” exist?

creatonez

10 hours ago

It's at the kernel level. Each process has its own current working directory. On Linux, these CWD values are exposed at `/proc/[...]/cwd`. This value affects the resolution of relative paths in filesystem operations at a syscall level.

hnlmorg

2 hours ago

It’s also generally a shell builtin. Though you do find an executable called cd too for compatibility reasons.

jasomill

29 minutes ago

Interesting. I've been using Unix systems for 30 years and never noticed this.

On my Fedora system, /usr/bin/cd is just a shell script that invokes the shell builtin:

  #!/usr/bin/sh
  builtin cd "$@"
I suppose it could be useful for testing whether a directory exists with search permissions for the current user safely in a multithreaded program that relies on the current directory remaining constant.

mattstir

an hour ago

Yeah, it's typically a shell built-in since you'd want cd to change the cwd for the shell process itself. Child processes (like commands being executed in the shell) can inherit the parent shell's cwd but AFAIK the opposite isn't true.

semiquaver

10 hours ago

Unix defines a Working Directory that every process has, changed with chdir(2): https://man7.org/linux/man-pages/man2/chdir.2.html

mort96

4 hours ago

This doesn't technically answer the question: POSIX doesn't concern itself with the kernel interface, only with the libc. Most POSIX systems have a kernel with a syscall interface that mirrors the libc API so that these libc functions are just syscall wrappers, but nothing technically prevents the current working directory to be a purely userspace concept maintained by the libc where all relative paths passed to filesystem functions are translated into absolute paths by the libc function before being passed to the kernel via syscall.

But yes, in the BSDs, Linux and Windows, the kernel has a concept of a current working directory.

mort96

29 minutes ago

Is this getting downvoted only because I referred to POSIX rather than UNIX? I'm more familiar with POSIX, but I'm 99% sure the UNIX standard also doesn't say anything about the kernel interface...

MobiusHorizons

11 hours ago

Very cool. Good use of quickjs, although it would have been cool if it somehow didn’t need a libc and just used the syscall interface. Makes me want to give that a try.

nxobject

8 hours ago

Kernighan and Ritchie wept. (Tears of joy at an awesome hack, or tears of sadness at an awesome hack?)

anthk

4 hours ago

I remember some core Unix utilities reimplemented in Perl, mainly done for Win32 systems back in the day. OFC the performance coudn't compete with the ones written in C, but it was good enough.

stevekemp

2 hours ago

You're thinking of the Perl Power Tools:

https://github.com/briandfoy/PerlPowerTools

I guess there are related projects such as busybox which contain a collection of utilities implemented in a single binary. There are others such as toybox, and various alternatives in different languages, or with different licenses to choose from.

hxbdbehd

6 hours ago

Many comments here seem to miss the point: this is not running the Linux Kernel in JavaScript

This is the Linux Userland reimplemented in JavaScript

darkreader

6 hours ago

strange motivation and implementation. I mean it real. There are many existing open source projects that run Linux on JS.