sbrk


SYNOPSIS
       #include <unistd.h>

       int brk(void *addr);

       void *sbrk(intptr_t increment);

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

       brk(), sbrk():
           Since glibc 2.12:
               _BSD_SOURCE || _SVID_SOURCE ||
                   (_XOPEN_SOURCE >= 500 ||
                       _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
                   !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
           Before glibc 2.12:
               _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
               _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

DESCRIPTION
       brk() and sbrk() change  the  location  of  the  program  break,  which
       defines  the end of the process's data segment (i.e., the program break
       is the first location after the end of the uninitialized data segment).
       Increasing the program break has the effect of allocating memory to the
       process; decreasing the break deallocates memory.

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

       sbrk() increments the program's data space by increment bytes.  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 the previous program break.  (If the break
       was increased, then this value is a pointer to the start of  the  newly
       allocated memory).  On error, (void *) -1 is returned, and errno is set
       to ENOMEM.

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

NOTES
       Avoid using brk() and sbrk(): the malloc(3) memory  allocation  package
       is the portable and comfortable way of allocating memory.

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

       return the old break value.

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

COLOPHON
       This  page  is  part of release 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://man7.org/linux/man-pages/.



Linux                             2010-09-20                            BRK(2)
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