V10/man/man2/brk.2

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.TH BRK 2
.CT 2 mem_man
.SH NAME
brk, sbrk \(mi change core allocation
.SH SYNOPSIS
.nf
.B int brk(addr)
.B char *addr;
.PP
.B char *sbrk(incr)
.fi
.SH DESCRIPTION
.I Brk
sets the system's idea of the lowest location not used by the program
(called the break)
to
.I addr
rounded up to the next multiple of 1024 bytes.
Locations not less than
.I addr
and below the stack pointer
may cause a memory violation if accessed.
.PP
In the alternate function
.I sbrk,
.I 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
.I brk,
but a nominal break is remembered, so rounding does not accumulate.
.PP
When a program begins execution via
.I 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
.IR brk .
.PP
The error return from
.I sbrk
is
.BR "(char *)-1" .
.SH "SEE ALSO"
.IR exec (2),
.IR end (3),
.IR malloc (3)
.SH DIAGNOSTICS
.B ENOMEM