.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved. The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\" @(#)brk.2 6.4 (Berkeley) 6/17/86
.TH BRK 2 "June 17, 1986"
brk, sbrk \- change data segment size
sets the system's idea of the lowest data segment
location not used by the program (called the break)
(rounded up to the next multiple of the system's page size).
and below the stack pointer
are not in the address space and will thus
cause a memory violation if accessed.
In the alternate function
more bytes are added to the
program's data space and a pointer to the
start of the new area is returned.
When a program begins execution via
highest location defined by the program
Ordinarily, therefore, only programs with growing
The current value of the program break is reliably returned by
system call may be used to determine
the maximum permissible size of the
it will not be possible to set the break
value returned from a call to
e.g. \*(lqetext + rlp\(->rlim_max.\*(rq
\-1 if the program requests more
memory than the system limit.
returns \-1 if the break could not be set.
will fail and no additional memory will be allocated if
one of the following are true:
The maximum possible size of a data segment (compiled into the
Insufficient space existed in the swap area
to support the expansion.
execve(2), getrlimit(2), malloc(3), end(3)
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