[LUNI] rm help

[Keith T. Garner]

On Tue, Jun 17, 2003 at 02:28:28, Steve Johnson said:
> I've written a few cli apps and the two are definately handled 
> differently.  You do have to specify arguments individually in your app,
> or use a library to handle unlimited args for you. but I still think
> there may be a limit for args, as for stdin, i think it's based on you
> terminal programs limitations. 

The arg limit has nothing to do with your terminal program at all.
It's actually a limitation defined by the kernel.

Its defined in the include file <linux/limits.h>  The line with this
is:

#define ARG_MAX       131072    /* # bytes of args + environ for exec() */

But that specifies in bytes how big that arg structure can be in
bytges as well as the space for the environment.  (I forgot to mention
a third thing is passed to each C main, and thats an array of strings
that has all your environmental variables.)

On my friends OpenBSD box, there is a define named _POSIX_ARG_MAX which
says you can have 4096 arguments.  However, OpenBSD tops out
at much more, as does Linux.

Ah, found another reference in linux/binfmts.h

/*
 * MAX_ARG_PAGES defines the number of pages allocated for arguments
 * and envelope for the new program. 32 should suffice, this gives
 * a maximum env+arg of 128kB w/4KB pages!
 */
#define MAX_ARG_PAGES 32

So, basically, there isn't a hard number, but there is a upper bounds
in memory.

Keith

-- 
   Keith T. Garner                                        kgarner at kgarner.com
   The whole problem with the world is that fools and fanatics are always so
 certain of themselves, and wiser people so full of doubts.  --Bertrand Russell