82
Presenting: SUDO for DOS (codeberg.org)
submitted 8 months ago by to c/programmer_humor@programming.dev
21 comments fedilink hide all child comments
 

An implementation of sudo for DOS, to run the given command with full privileges. It can be used to edit important system files, run disk partitioning tools, and so on!

you are viewing a single comment's thread
view the rest of the comments
[–] 16 points 8 months ago* (4 children)

Fun fact: all Windows exe files are also com files. They all have a dos running part, most of which simply prints "this program cannot be run in dos mode" and exits, but some programs do have fully functional dos program as well as the usual windows GUI part, all in one exe.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 4 child comments
    •
  • [–] 11 points 8 months ago* (1 child)

    Technically that segment is not a com file. They are MZ exe files. com files have no metadata or header.

    There are actually 3 exe variants, MZ, NE, and the modern PE

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 1 child comment
    •
  • [–] 3 points 8 months ago (1 child)

    I actually first thought that was weird and wasteful. Then I remembered that, uh, Commodore 64 often uses a similar thing. Basically, a lot of assembly and compiled languages just put the machine code into the BASIC memory, preceded by a stub BASIC program that's basically just "10 SYS addr" with that address pointing just past the end of the stub program itself. BASIC's LOAD command handles it just fine because program files don't have any header information besides load address. BASIC handles the loaded program just normally because the program has the end token, so as long as you don't modify the BASIC program, it'll be fine.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 1 child comment
    •
  • [–] [S] 3 points 8 months ago

    Luckily the .exe's MZ header is pretty small. But in this case it was necessary: when DOS loads a .com binary, it can't know how much memory it will need, so DOS just gives it all free memory. But then the program can't launch another, because all memory is in use. So that's why I had to add the MZ header which allows specifying the memory needs.

  • permalink
  • fedilink
  • source
  • parent