BRK(2) BRK(2)
NAME
brk, sbrk, break - change core allocation
SYNOPSIS
char *brk(addr)
char *sbrk(incr)
DESCRIPTION
Brk sets the system's idea of the lowest location not used
by the program (called the break) to addr (rounded up to the
next multiple of 64 bytes on a PDP11 and 1024 bytes on a
VAX). Locations not less than addr and below the stack
pointer are not in the address space and will thus cause a
memory violation if accessed.
In the alternate function sbrk, incr more bytes are added to
the program's data space and a pointer to the start of the
new area is returned. (Rounding occurs as with brk, but a
nominal break is remembered, so rounding does not accumu-
late.)
When a program begins execution via exec the break is set at
the highest location defined by the program and data storage
areas. Ordinarily, therefore, only programs with growing
data areas need to use break.
SEE ALSO
exec(2), malloc(3), end(3)
DIAGNOSTICS
Zero is returned if the brk could be set; -1 if the program
requests more memory than the system limit or if too many
segmentation registers would be required to implement the
break. Sbrk returns -1 if the break could not be set.