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C's system() & COMMAND.COM (Developers)

posted by alexfru, USA, 16.09.2014, 23:24

> > DJGPP looks at the extension and executes .COM/.EXE directly if the
> > extension is present.
> >
> > OW seems to do that and also consult a list of what it thinks are
> > COMMAND.COM's commands.
> >
> > For me checking the extension and possibly traversing PATH is good
> enough.
>
> All very dangerous roads to go down, especially with things like 4DOS
> around (aliases, BTM files, etc.). Even MS-DOS has an extensibility
> function (INT 2F.AE00/AE01) that allows you to effectively add your own
> "internal" commands (via TSR's) to the ones built into the shell.
> Basically, you can never be certain what all of the "internal" commands
> (which get processed before any executable file even if they have the same
> name) really are.
>
> Internal commands are ALWAYS processed first, so even if you find a valid
> COM/EXE/BAT/BTM with the appropriate name, it may not be what actually gets
> processed.
If I execute a .COM/.EXE directly (int 21h function 4b00h) and not via "%COMSPEC% /C", it should just work, no matter what internal commands are.

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