BRK(2)			   Linux Programmer's Manual			BRK(2)



NAME
       brk, sbrk - change data segment size

SYNOPSIS
       #include <unistd.h>

       int brk(void *end_data_segment);

       void *sbrk(intptr_t increment);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       brk(), sbrk(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       brk()  sets  the  end  of  the  data  segment to the value specified by
       end_data_segment, when that value is reasonable, the system  does  have
       enough  memory  and  the process does not exceed its max data size (see
       setrlimit(2)).

       sbrk() increments the program's data space by increment bytes.	sbrk()
       isn't  a  system  call, it is just a C library wrapper.	Calling sbrk()
       with an increment of 0 can be used to find the current location of  the
       program break.

RETURN VALUE
       On success, brk() returns zero.	On error, -1 is returned, and errno is
       set to ENOMEM.  (But see Linux Notes below.)

       On success, sbrk() returns a pointer to the start of the new area.   On
       error, -1 is returned, and errno is set to ENOMEM.

CONFORMING TO
       4.3BSD; SUSv1, marked LEGACY in SUSv2, removed in POSIX.1-2001.

       brk() and sbrk() are not defined in the C Standard and are deliberately
       excluded from  the  POSIX.1  standard  (see  paragraphs	B.1.1.1.3  and
       B.8.3.3).

NOTES
       Various	systems use various types for the parameter of sbrk().	Common
       are int, ssize_t, ptrdiff_t, intptr_t.

   Linux Notes
       The return value described above for brk() is the behavior provided  by
       the  glibc  wrapper function for the Linux brk() system call.  (On most
       other implementations, the return value from brk() is the same.)   How-
       ever,  the  actual  Linux  system call returns the new program break on
       success.  On failure, the system call returns the current  break  (thus
       for  example, the call brk(0) can be used to obtain the current break).
       The glibc wrapper function does some work  to  provide  the  0  and  -1
       return values described above.

       On  Linux,  sbrk()  is  implemented as a library function that uses the
       brk() system call, and does some internal bookkeeping so  that  it  can
       return the old break value.

SEE ALSO
       execve(2), getrlimit(2), malloc(3)

COLOPHON
       This  page  is  part of release 2.77 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



Linux				  2007-07-26				BRK(2)