JSLinux utils

This repo contains reverse-engineered sources for utilities found in Fabrice Bellard's JSLinux images.

JSLinux uses filesystem images served from vfsync.org.

Image Alpine Linux 3.23.2

TinyEMU config: https://bellard.org/jslinux/alpine-x86_64.cfg

Filesystem: https://vfsync.org/u/os/alpine-x86_64

localhost:~# ls -l /usr/local/bin
total 900
-rwxr-xr-x    1 root     root        341992 Jan 13  2026 bfcalc
-rwxr-xr-x    1 root     root         18248 Jan 12  2026 export_file
-rwxr-xr-x    1 root     root        190440 Mar 11 14:39 mqjs
-rwxr-xr-x    1 root     root        194536 Mar 11 14:38 mqjs_apx
lrwxrwxrwx    1 root     root            11 Jan 12  2026 set_import_dir -> export_file
-rwxr-xr-x    1 root     root         14072 Jan 12  2026 settime
-rwxr-xr-x    1 root     root         18248 Jan 13  2026 tinypi
-rwxr-xr-x    1 root     root         18168 Jan 12  2026 vfagent
-rwxr-xr-x    1 root     root         18248 Jan 12  2026 vflogin
-rwxr-xr-x    1 root     root         67640 Jan 12  2026 vfsync
-rwxr-xr-x    1 root     root         14152 Jan 12  2026 vmtime

export_file and set_import_dir

See export_file/README.md.

tinypi

See https://bellard.org/pi/tinypi/

mqjs and mqjs_apx

See github.com/bellard/mquickjs.

vfagent, vflogin, vfsync

See vfsync.org.

Sources: https://vfsync.org/vfsync-2017-05-21.tar.gz

bfcalc

localhost:~# bfcalc -h
usage: bfcalc [options] [filename]
-h        help
-H        hex display
-j        use JS operator syntax ('^' is xor instead of power)
-t        built-in autotest
-e expr   evaluate the expression 'expr'
 
Type '\h' for help in interactive mode
localhost:~# bfcalc
bfcalc > 3+4
7
bfcalc > 21*5
105
bfcalc > sqrt(2)
1.414213562373095
bfcalc > \h
\h          this help
\h func     show more information about built-in function 'func'
\h units    show the available units
\x          hexadecimal number display
\d          decimal number display
\js         toggle Javascript mode ('^' is xor instead of power, [] is an array literal instead of tensor)
bfcalc > ^D