FEBUG(8) System Manager's Manual FEBUG(8)

febug
User-space debugfs filesystem driver

febug [
-hV
] [
libfuse options
] mountpoint

febug mounts a filesystem at mountpoint that allows programs to register themselves and expose variables to be (relatively) non-intrusively inspected at run-time, inspired by the debugfs filesystem.
See febug-abi(8) for implementation details. And the EXAMPLES section for an example debug session.

-h or --help and -V or --version are self-explanatory.
febug passes all arguments (which have to, therefore, include mountpoint) to fuse_main(3), with -f (foreground) and -o default_permissions appended. If run with effective UID of 0, it also appends -o allow_other.

FEBUG_SOCKET the socket at which to listen for programs, or /run/febug.sock by default.

# systemctl start febug 
$ findmnt /run/febug 
/run/febug febug fuse.febug rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other 
$ ./out/examples/vector-sort & 
[1] 1409 
$ LD_LIBRARY_PATH=out ./out/examples/string-qsort & 
[2] 1410 
$ ls /run/febug/ 
1409 1410 
$ ls -l /run/febug/ 
dr-xr-x--- 4 nabijaczleweli users 0 Jan 15 19:52 1409 
dr-xr-x--- 3 nabijaczleweli users 0 Jan 15 19:52 1410 
$ ls /run/febug/1409/ 
comparisons cool_data 
$ cat /run/febug/1409/* 
24 
-3 -2 -3 -2 -3 -2 3 -1 -2 -3 0 1 2 3 -1 -2 -3 0 1 2 3 -1 -2 -3 0 1 2 3 -1 2 1 0 1 2 3 -1 0 -1 0 1 2 3 
$ cat /run/febug/1409/* 
45 
-3 -2 -3 -2 -3 -2 -3 -2 -2 -3 -3 -2 -1 3 -1 1 0 0 1 2 3 2 -1 3 0 1 2 3 -1 2 1 0 1 2 3 -1 0 -1 0 1 2 3 
$ grep . /run/febug/*/* 
/run/febug/1409/comparisons:71 
/run/febug/1409/cool_data:-3 -3 -3 -3 -3 -3 -2 -2 -2 -2 -2 -2 -1 3 -1 1 0 0 1 2 3 2 -1 3 0 1 2 3 -1 2 1 0 1 2 3 -1 0 -1 0 1 2 3 
/run/febug/1410/cool_data:3012987654ACEFOLJKODNIEMIGHBPPbdWwnfTpXQcreRlVvUSitZQWjRTYUazuqwertyuiopoxyhmYsgkq 
$ kill %1 
$ ls /run/febug/ 
1410

febug-abi(5) — the ABI used to connect with this filesystem.
libfebug(3) — a library wrapping this ABI.
libfebug++(3) — a C++ library wrapping this ABI.

Written by наб <nabijaczleweli@nabijaczleweli.xyz>

To all who support further development, in particular:

febug tracker
febug mailing list: <~nabijaczleweli/febug@lists.sr.ht> archived at https://lists.sr.ht/~nabijaczleweli/febug
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