Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!pasteur!ames!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: comp.unix.questions
Message-ID: <9942@smoke.BRL.MIL>
Date: 29 Mar 89 15:58:16 GMT
References: <55125@yale-celray.yale.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Followup-To: comp.unix.questions
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 16

In article <55125@yale-celray.yale.UUCP> chen-dahe@CS.Yale.EDU (Dahe Chen) writes:
>Can anyone tell me a way to find out hwo much memory a C program is
>using at a certain point. I tried with dbx and ps. It seems ps only
>gives the maximum size of memory ever used. Am I right?

This is apparently a UNIX-specific question and really has little to
do with C.  On UNIX, a process typically has a fixed amount of "text"
(instruction) space, a variable (fixed on some architectures) amount
of stack space for activation records, a fixed amount of preinitialized
data space, and a variable amount of "heap" (dynamic) memory space.
The latter is where memory assigned by the C library malloc() routine
comes from.  When a process needs more dynamic memory, it requests that
its heap space be grown by the operating system, via a sbrk() or brk()
system call.  (malloc() does that when necessary.)  There is really no
notion of how much of the current heap space is "used" or "unused"; it
is all available to your process.  That's what is reported by "ps" etc.