VLIMIT(3C)

NAME
vlimit - control maximum system resource consumption

SYNOPSIS
#include <sys/vlimit.h>

vlimit(resource, value) int resource, value;

DESCRIPTION

This facility is superseded by getrlimit(2).

Limits the consumption by the current process and each process it creates to not individually exceed value on the specified resource. If value is specified as -1, then the current limit is returned and the limit is unchanged. The resources which are currently controllable are:

LIM_NORAISE
    A pseudo-limit; if set non-zero then the limits may not be raised. Only the super-user may remove the noraise restriction.

LIM_CPU
    the maximum number of CPU-seconds to be used by each process

LIM_FSIZE
    the largest single file which can be created

LIM_DATA
    the maximum growth of the data+stack region using sbrk() (see brk(2)) beyond the end of the program text

LIM_STACK
    the maximum size of the automatically-extended stack region

LIM_CORE
    the size of the largest core dump that will be created.

LIM_MAXRSS
    a soft limit for the amount of physical memory (in bytes) to be given to the program. If memory is tight, the system will prefer to take memory from processes which are exceeding their declared LIM_MAXRSS.

Because this information is stored in the per-process information this system call must be executed directly by the shell if it is to affect all future processes created by the shell; limit is thus a built-in command to csh(1).

The system refuses to extend the data or stack space when the limits would be exceeded in the normal way; a break call fails if the data space limit is reached, or the process is killed when the stack limit is reached (since the stack cannot be extended, there is no way to send a signal!).

A file I/O operation which would create a file which is too large will cause a signal SIGXFSZ to be generated, this normally terminates the process, but may be caught. When the cpu time limit is exceeded, a signal SIGXCPU is sent to the offending process; to allow it time to process the signal it is given 5 seconds grace by raising the CPU time limit.

SEE ALSO
csh(1), sh(1), brk(2)

BUGS

If LIM_NORAISE is set, then no grace should be given when the CPU time limit is exceeded.

There should be limit and unlimit commands in sh(1) as well as in csh(1).