Busybox TODO Stuff that needs to be done tr - missing SuS3 features in busybox 1.0pre10 tr doesnt support [:blank:], [:digit:] or other predefined classes, [=equiv=] support is also missing. ---- find doesn't understand () or -exec, and these are actually used out in the real world. The "make uninstall" of lots of things (including busybox itself) breaks because of this, and sometimes even "make install" (like udev). ---- sh The command shell situation is a big mess. We have three or four different shells that don't really share any code, and the "standalone shell" doesn't work all that well (especially not in a chroot environment), due to apps not being reentrant. Unifying the various shells and figuring out a configurable way of adding the minimal set of bash features a given script uses is a big job, but it be a big improvement. Note: Rob Landley (rob@landley.net) is working on this one, but very slowly... --- gzip Can't handle compressing multiple files at once. (I don't mean making a multiple file archive, I mean compressing more than one file at a time.) Some global variables aren't re-initialized between runs. --- gunzip same problem as gzip. "gunzip one.gz two.gz three.gz" doesn't work for two.gz and three.gz due to global variables not getting reset. --- diff We should have a diff -u command. We have patch, we should have diff (we only need to support unified diffs though). --- fuser Would be nice. The basic susv3 options, plus fuser -k. --- patch should have simple fuzz factor support to apply patches at an offset which shouldn't take up too much space. --- man It would be nice to have a man command. Not one that handles troff or anything, just one that can handle preformatted ascii man pages, possibly compressed. This could probably be a script in the extras directory that calls cat/zcatbzcat | more --- bzip2 Compression-side support. Architectural issues: Do a SUSv3 audit Look at the full Single Unix Specification version 3 (available online at "http://www.opengroup.org/onlinepubs/009695399/nfindex.html") and figure out which of our apps are compliant, and what we're missing that we might actually care about. Even better would be some kind of automated compliance test harness that exercises each command line option and the various corner cases. -- Unify archivers Lots of archivers have the same general infrastructure. The directory traversal code should be factored out, and the guts of each archiver could be some setup code and a series of callbacks for "add this file", "add this directory", "add this symlink" and so on. This could clean up tar and zip, and make it cheaper to add cpio and ar write support, and possibly even cheaply add things like mkisofs someday, if it becomes relevant. --- Text buffer support. Several existing applets and potential additions (sort, vi, less...) read a whole file into memory and act on it. There might be an opportunity for shared code in there that could be moved into libbb... --- Individual compilation of applets. It would be nice if busybox had the option to compile to individual applets, for people who want an alternate implementation less bloated than the gnu utils (or simply with less political baggage), but without it being one big executable. Turning libbb into a real dll is another possibility, especially if libbb could export some of the other library interfaces we've already more or less got the code for (like zlib). --- buildroot - Make a "dogfood" option Busybox is now capable of replacing most gnu packages for real world use, such as developing software or in a live CD. A system built from busybox (1.00 with updated sort.c), uclibc 0.9.27, gcc, binutils, make, and a few other development tools (http://www.landley.net/code/firmware has an example system using autoconf, automake, bison, flex, libtools, m4, zlib, and groff: dunno what subset of that is actually necessary) is capable of rebuilding itself, from scratch, under itself. It would be a good "eating our own dogfood" test if buildroot had the option of using busybox instead of bzip2, coreutils, file, findutils, gawk, grep, inetutils, modutils, net-tools, procps, sed, shadow, sysklogd, sysvinit, tar, util-linux, and vim. Anything that's wrong with the resulting system, we can fix. (It would be nice to be able to upgrade busybox to be able to replace bash, diffutils, gzip, less, and patch as well.) --- Memory Allocation We have a CONFIG_BUFFER mechanism that lets us select whether to do memory allocation on the stack or the heap. Unfortunately, we're not using it much. We need to audit our memory allocations and turn a lot of malloc/free calls into RESERVE_CONFIG_BUFFER/RELEASE_CONFIG_BUFFER. And while we're at it, many of the CONFIG_FEATURE_CLEAN_UP #ifdefs will be optimized out by the compiler in the stack allocation case (since there's no free for an alloca()), and this means that various cleanup loops that just call free might also be optimized out by the compiler if written right, so we can yank those #ifdefs too, and generally clean up the code. --- Switch CONFIG_SYMBOLS to ENABLE_SYMBOLS In busybox 1.0 and earlier, configuration was done by CONFIG_SYMBOLS that were either defined or undefined to indicate whether the symbol was selected in the .config file. They were used with #ifdefs, ala: #ifdef CONFIG_SYMBOL if (other_test) { do_code(); } #endif In 1.1, we have new ENABLE_SYMBOLS which are always defined (as 0 or 1), meaning you can still use them for preprocessor tests by replacing "#ifdef CONFIG_SYMBOL" with "#if ENABLE_SYMBOL". But more importantly, we can use them as a true or false test in normal C code: if (ENABLE_SYMBOL && other_test) { do_code(); } (Optimizing away if() statements that resolve to a constant value is known as "dead code elimination", an optimization so old and simple that Turbo Pascal for DOS did it twenty years ago. Even modern mini-compilers like the Tiny C Compiler (tcc) and the Small Device C Compiler (SDCC) perform dead code elimination.) Right now, busybox.h is #including both "config.h" (defining the CONFIG_SYMBOLS) and "bb_config.h" (defining the ENABLE_SYMBOLS). At some point in the future, it would be nice to wean ourselves off of the CONFIG versions. (Among other things, some defective build environments leak the Linux kernel's CONFIG_SYMBOLS into the system's standard #include files. We've experienced collisions before.) --- FEATURE_CLEAN_UP This is more an unresolved issue than a to-do item. More thought is needed. Normally we rely on exit() to free memory, close files, and unmap segments for us. This makes most calls to free(), close(), and unmap() optional in busybox applets that don't intend to run for very long, and optional stuff can be omitted to save size. The idea was raised that we could simulate fork/exit with setjmp/longjmp for _really_ brainless embedded systems, or speed up the standalone shell by not forking. Doing so would require a reliable FEATURE_CLEAN_UP. Unfortunately, this isn't as easy as it sounds. The problem is, lots of things exit(), sometimes unexpectedly (xmalloc()) and sometimes reliably (bb_perror_msg_and_die() or show_usage()). This jumps out of the normal flow control and bypasses any cleanup code we put at the end of our applets. It's possible to add hooks to libbb functions like xmalloc() and bb_xopen() to add their entries to a linked list, which could be traversed and freed/closed automatically. (This would need to be able to free just the entries after a checkpoint to be usable for a forkless standalone shell. You don't want to free the shell's own resources.) Right now, FEATURE_CLEAN_UP is more or less a debugging aid, to make things like valgrind happy. It's also documentation of _what_ we're trusting exit() to clean up for us. But new infrastructure to auto-free stuff would render the existing FEATURE_CLEAN_UP code redundant. For right now, exit() handles it just fine.