ulimit

Purpose

     Sets and gets user limits.

Syntax

     #include <sys/types.h>

     off_t ulimit (cmd, newlimit)
     int cmd;
     off_t newlimit;

Description

     The ulimit system call  controls process limits.  The cmd
     parameter values are:

     1      Returns the process's file  size limit.  The limit
            is in units of 512-byte blocks and is inherited by
            child processes.  Files of any size can be read.

     2      Sets the process's file size limit to the value of
            the newlimit parameter.   Any process can decrease
            this limit,  but only a process  with an effective
            user ID of superuser can increase the limit.

     3      Returns  the  maximum  possible break  value  (see
            "brk, sbrk").

     1004   Sets the  maximum possible break value  (see "brk,
            sbrk").   Returns  the  new maximum  break  value,
            which is  newlimit rounded up to  the nearest page
            boundary.

     1005   Returns  the lowest  valid  stack address.   (Note
            that  stacks  grow  from  high  addresses  to  low
            addresses.)

     1006   Sets the lowest valid  stack address.  Returns the
            new minimum valid stack address, which is newlimit
            rounded down to the nearest page boundary.

     With remote  files, the ulimit  values of the  client, or
     local, node are used.

Return Value

     Upon  successful  completion,   a  nonnegative  value  is
     returned.  If the ulimit system call fails, a value of -1
     is returned and errno is set to indicate the error.

Diagnostics

     The  ulimit  system  call  fails and  the  limit  remains
     unchanged if:

     EPERM      A process with an effective user ID other than
                superuser attempts  to increase the  file size
                limit.

     EINVAL     The cmd parameter is a  value other than 1, 2,
                or 3.

Example

     To increase the size of  the stack segment by 2048 bytes,
     and set "rc" to the new lowest valid stack address:

       rc = ulimit(1006, ulimit(1005, 0) - 2048);

Related Information

     In this book:  "brk, sbrk" and "write, writex."