Creating Really Teensy ELF Executables for Linux

This article is surprisingly better (and longer ;) than I expected, but it skipped over explaining one important distinction; "ELF" is an executable file format, but "a.out" is more than just a default file name; it's also the name of a totally different executable file format.

Originally, the "a.out" executable format, and hence, the "a.out" file name were due to being the "assembler output" of Ken Thompson's assembler in 1968. Most all UNIX-based systems have moved to using newer ELF format, but there are a few hold-outs still using the older a.out format. As for why ELF formatted executable files are still given the file name "a.out" by default, even when they are not in the "a.out" executable format, it's just a historic artifact (or annoyance) due to compilers and linkers.

http://en.wikipedia.org/wiki/A.out

That's what I loved about DOS com executables. Possibly the smallest program was:

  int 20;

which got translated into CDh 20h (4 bytes!)

I'm impressed. The author did a lot of mangling to allow the code to be as small as possible. Other than ELF and a.out format, (which is discused by @jcr) I wonder if there are other formats understood by Linux ?

Nice. Perhaps have a look at uclibc and busybox... :-)

I was hoping that the final size would be 42 :)

Care to update for 64 bits?