BSD 2.11 - man page for brk (bsd section 2)

Linux & Unix Commands - Search Man Pages

Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


BRK(2)											   BRK(2)

NAME
       brk, sbrk - change data segment size

SYNOPSIS
       #include <sys/types.h>

       char *brk(addr)
       char *addr;

       char *sbrk(incr)
       int incr;

DESCRIPTION
       Brk  sets  the  system's  idea of the lowest data segment location not used by the program
       (called the break) to addr (rounded up to the next multiple of the  system's  page  size).
       Locations  greater  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.

       When  a	program  begins  execution  via  execve  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 sbrk.

       The  getrlimit(2) system call may be used to determine the maximum permissible size of the
       data segment; it will not be possible to set the break beyond the rlim_max value  returned
       from a call to getrlimit, e.g. "etext + rlp->rlim_max."	(see end(3) for the definition of
       etext).

RETURN VALUE
       Zero is returned if the brk could be set; -1 if the program requests more memory than  the
       system limit.  Sbrk returns -1 if the break could not be set.

ERRORS
       Sbrk  will  fail  and  no  additional memory will be allocated if one of the following are
       true:

       [ENOMEM]       The limit, as set by setrlimit(2), was exceeded.

       [ENOMEM]       The maximum possible size of a data segment (compiled into the system)  was
		      exceeded.

       [ENOMEM]       Insufficient space existed in the swap area to support the expansion.

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

BUGS
       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 getrlimit.

4th Berkeley Distribution		   May 22, 1986 				   BRK(2)
Unix & Linux Commands & Man Pages : ©2000 - 2018 Unix and Linux Forums


All times are GMT -4. The time now is 01:27 PM.

Unix & Linux Forums Content Copyright©1993-2018. All Rights Reserved.
×
UNIX.COM Login
Username:
Password:  
Show Password





Not a Forum Member?
Forgot Password?