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Minix/CD-ROM-2.0/MINIX/MANUALS/CAT2/BRK.2

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+BRK(2)                    Minix Programmer's Manual                     BRK(2)
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+NAME
+     brk, sbrk - change data segment size
+
+SYNOPSIS
+     #include <unistd.h>
+
+     char *brk(char *addr)
+
+     char *sbrk(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.  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.
+
+RETURN VALUE
+     The address of the new break is returned  if  brk  succeeds;  -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 maximum possible size of a data  segment  (as  set  by
+                    chmem(1)) was exceeded.
+
+     [ENOMEM]       Insufficient virtual memory space existed to  support  the
+                    expansion.  (Minix-vmd)
+
+SEE ALSO
+     chmem(1), execve(2), malloc(3), end(3).
+
+NOTES
+     Minix-vmd rounds a small data segment limit up to 3 megabytes.
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+4BSD                              May 22, 1986                               1
+
+
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+BRK(2)                    Minix Programmer's Manual                     BRK(2)
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+BUGS
+     Setting the break may fail due to a  temporary  lack  of  virtual  memory
+     under  Minix-vmd.   It is not possible to distinguish this from a failure
+     caused by exceeding the maximum size of the data segment.
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+4BSD                              May 22, 1986                               2
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