|
Hopefully, this page is exactly what you are looking for, but if not, you can always find further assistance on Unix/Linux Forum!
System Calls brk(2)
NAME
brk, sbrk - change the amount of space allocated for the
calling process's data segment
SYNOPSIS
#include <unistd.h>
int brk(void *endds);
void *sbrk(intptr_t incr);
DESCRIPTION
The brk() and sbrk() functions are used to change dynami-
cally the amount of space allocated for the calling
process's data segment (see exec(2)). The change is made by
resetting the process's break value and allocating the
appropriate amount of space. The break value is the address
of the first location beyond the end of the data segment.
The amount of allocated space increases as the break value
increases. Newly allocated space is set to zero. If, how-
ever, the same memory space is reallocated to the same pro-
cess its contents are undefined.
When a program begins execution using execve() the break is
set at the highest location defined by the program and data
storage areas.
The getrlimit(2) function may be used to determine the max-
imum permissible size of the data segment; it is not possi-
ble to set the break beyond the rlim_max value returned from
a call to getrlimit(), that is to say, "end +
rlim.rlim_max." See end(3C).
The brk() function sets the break value to endds and changes
the allocated space accordingly.
The sbrk() function adds incr function bytes to the break
value and changes the allocated space accordingly. The incr
function can be negative, in which case the amount of allo-
cated space is decreased.
RETURN VALUES
Upon successful completion, brk() returns 0. Otherwise, it
returns -1 and sets errno to indicate the error.
Upon successful completion, sbrk() returns the prior break
value. Otherwise, it returns (void *)-1 and sets errno to
indicate the error.
ERRORS
The brk() and sbrk() functions will fail and no additional
memory will be allocated if:
SunOS 5.10 Last change: 14 Jan 1997 1
System Calls brk(2)
ENOMEM The data segment size limit as set by
setrlimit() (see getrlimit(2)) would be
exceeded; the maximum possible size of a
data segment (compiled into the system)
would be exceeded; insufficient space exists
in the swap area to support the expansion;
or the new break value would extend into an
area of the address space defined by some
previously established mapping (see
mmap(2)).
EAGAIN Total amount of system memory available for
private pages is temporarily insufficient.
This may occur even though the space
requested was less than the maximum data
segment size (see ulimit(2)).
USAGE
The behavior of brk() and sbrk() is unspecified if an appli-
cation also uses any other memory functions (such as
malloc(3C), mmap(2), free(3C)). The brk() and sbrk() func-
tions have been used in specialized cases where no other
memory allocation function provided the same capability.
The use of mmap(2) is now preferred because it can be used
portably with all other memory allocation functions and with
any function that uses other allocation functions.
It is unspecified whether the pointer returned by sbrk() is
aligned suitably for any purpose.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
SEE ALSO
exec(2), getrlimit(2), mmap(2), shmop(2), ulimit(2),
end(3C), free(3C), malloc(3C)
NOTES
The value of incr may be adjusted by the system before set-
ting the new break value. Upon successful completion, the
SunOS 5.10 Last change: 14 Jan 1997 2
System Calls brk(2)
implementation guarantees a minimum of incr bytes will be
added to the data segment if incr is a positive value. If
incr is a negative value, a maximum of incr bytes will be
removed from the data segment. This adjustment may not be
necessary for all machine architectures.
The value of the arguments to both brk() and sbrk() are
rounded up for alignment with eight-byte boundaries.
BUGS
Setting the break may fail due to a temporary lack of swap
space. It is not possible to distinguish this from a failure
caused by exceeding the maximum size of the data segment
without consulting getrlimit().
SunOS 5.10 Last change: 14 Jan 1997 3
Man(1) output converted with
man2html and wrapped by fishsponge
This page was generated on Wed Sep 12 11:26:55 GMT 2007
|
Your favourite pages:
No pages logged yet.
Trying to save cookie... Top 10 most popular pages:
sqlite3 man page (5334 hits)
(openSUSE 10.2)
svn man page (5209 hits)
(FreeBSD 6.2)
adv_cap_autoneg man page (4870 hits)
(Solaris 10 11_06)
CPAN man page (4607 hits)
(Suse Linux 10.1)
ssh man page (4342 hits)
(Suse Linux 10.1)
ssh-socks5-proxy-connect man page (2884 hits)
(Solaris 10 11_06)
netcat man page (2717 hits)
(Suse Linux 10.1)
pprosetup man page (2492 hits)
(Solaris 10 11_06)
startproc man page (2471 hits)
(Suse Linux 10.1)
signal man page (2408 hits)
(Suse Linux 10.1)
|
Man Pages 
