The ulimit(2) function provides for control over process
limits. The cmd values, defined in <ulimit.h>
include:
UL_GDESLIM
Return the processes current soft limit for open file
descriptors.
UL_GETFSIZE
Return the soft file size limit of the process. The limit is in
units of 512-byte blocks and is inherited by child processes. Files
of any size can be read. The return value is the integer part of
the soft file size limit divided by 512. If the result cannot be
represented as a long int, the result is unspecified.
UL_SETFSIZE
Set the hard and soft file size limits for output operations of
the process to the value of the second argument, taken as a long
int. Any process may decrease its own hard limit, but only a
process with appropriate privileges may increase the limit. The new
file size limit is returned. The hard and soft file size limits are
set to the specified value multiplied by 512. If the result would
overflow an rlim_t, the actual value set is
unspecified.
Upon successful completion, ulimit(2) returns the value
of the requested limit. Otherwise -1 is returned and errno
is set to indicate the error. The ulimit(2) function will
not change the setting of errno if successful.
As all return values are permissible in a successful situation,
an application wishing to check for error situations should set
errno to 0, then call ulimit(2), and, if it returns
-1, check to see if errno is non-zero.