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Date: Tue, 14 Jan 2003 16:21:13 -0500
From: Mark Mielke <mark@mark.mielke.cc>
To: "Richard B. Johnson" <root@chaos.analogic.com>
Cc: DervishD <raul@pleyades.net>, Linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Changing argv[0] under Linux.
Message-ID: <20030114212113.GF15412@mark.mielke.cc>
References: <20030114202359.GD15412@mark.mielke.cc> <Pine.LNX.3.95.1030114152443.13840C-100000@chaos.analogic.com>
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On Tue, Jan 14, 2003 at 03:28:23PM -0500, Richard B. Johnson wrote:
> On Tue, 14 Jan 2003, Mark Mielke wrote:
> > On Tue, Jan 14, 2003 at 02:56:35PM -0500, Richard B. Johnson wrote:
> > > Well I just grepped through usr/include/bits/posix1_lim.h and it
> > > shows 255 (with this 'C' library) so you are probably right.
> > > In any event, a "whole line of text" isn't going to overrun it. 
> > Looking at the code, it looks to me as if argv[0] can be any size up to
> > _SC_ARG_MAX, with the restraining factor being that the environment
> > variables and the other arguments must fit in the same space.
> > Is this not correct?
> Don't think so. In my headers _SC_ARG_MAX is an enumerated type
> that is numerically equal to 0. It's in confname.h, the first
> element in the enumerated list.

_SC_ARG_MAX is one of the identifiers that are used with sysconf() to
lookup a system-wide configuration value:

    $ perl -MPOSIX -e 'print sysconf(_SC_ARG_MAX), "\n"'
    131072

The environment size for a program invoked using exec() can be up to
131072 bytes long (my configuration). This environment holds the
command arguments as well as the environment.

On my system, _SC_ARG_MAX is telling me that it is possible to have
argv[0] be just under 131072 bytes long.

mark

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