.\" $OpenBSD: getrlimit.2,v 1.8 1999/05/23 14:10:52 aaron Exp $ .\" $NetBSD: getrlimit.2,v 1.8 1995/10/12 15:40:58 jtc Exp $ .\" .\" Copyright (c) 1980, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93 .\" .Dd June 4, 1993 .Dt GETRLIMIT 2 .Os .Sh NAME .Nm getrlimit , .Nm setrlimit .Nd control maximum system resource consumption .Sh SYNOPSIS .Fd #include .Fd #include .Fd #include .Ft int .Fn getrlimit "int resource" "struct rlimit *rlp" .Ft int .Fn setrlimit "int resource" "const struct rlimit *rlp" .Sh DESCRIPTION Limits on the consumption of system resources by the current process and each process it creates may be obtained with the .Fn getrlimit call, and set with the .Fn setrlimit call. .Pp The .Fa resource parameter is one of the following: .Bl -tag -width RLIMIT_FSIZEAA .It Li RLIMIT_CORE The largest size (in bytes) .Pa core file that may be created. .It Li RLIMIT_CPU The maximum amount of cpu time (in seconds) to be used by each process. .It Li RLIMIT_DATA The maximum size (in bytes) of the data segment for a process; this defines how far a program may extend its break with the .Xr sbrk 2 system call. .It Li RLIMIT_FSIZE The largest size (in bytes) file that may be created. .It Li RLIMIT_MEMLOCK The maximum size (in bytes) which a process may lock into memory using the .Xr mlock 2 function. .It Li RLIMIT_NOFILE The maximum number of open files for this process. .It Li RLIMIT_NPROC The maximum number of simultaneous processes for this user id. .It Li RLIMIT_RSS The maximum size (in bytes) to which a process's resident set size may grow. This imposes a limit on the amount of physical memory to be given to a process; if memory is tight, the system will prefer to take memory from processes that are exceeding their declared resident set size. .It Li RLIMIT_STACK The maximum size (in bytes) of the stack segment for a process; this defines how far a program's stack segment may be extended. Stack extension is performed automatically by the system. .El .Pp A resource limit is specified as a soft limit and a hard limit. When a soft limit is exceeded a process may receive a signal (for example, if the cpu time or file size is exceeded), but it will be allowed to continue execution until it reaches the hard limit (or modifies its resource limit). The .Em rlimit structure is used to specify the hard and soft limits on a resource, .Bd -literal -offset indent struct rlimit { rlim_t rlim_cur; /* current (soft) limit */ rlim_t rlim_max; /* hard limit */ }; .Ed .Pp Only the super-user may raise the maximum limits. Other users may only alter .Fa rlim_cur within the range from 0 to .Fa rlim_max or (irreversibly) lower .Fa rlim_max . .Pp An .Dq infinite value for a limit is defined as .Dv RLIM_INFINITY . .Pp 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; .Ic limit is thus a built-in command to .Xr csh 1 and .Ic ulimit is the .Xr sh 1 equivalent. .Pp The system refuses to extend the data or stack space when the limits would be exceeded in the normal way: a .Xr brk 2 call fails if the data space limit is reached. When the stack limit is reached, the process receives a segmentation fault .Pq Dv SIGSEGV ; if this signal is not caught by a handler using the signal stack, this signal will kill the process. .Pp A file I/O operation that would create a file larger that the process' soft limit will cause the write to fail and a signal .Dv SIGXFSZ to be generated; this normally terminates the process, but may be caught. When the soft cpu time limit is exceeded, a signal .Dv SIGXCPU is sent to the offending process. .Sh RETURN VALUES A 0 return value indicates that the call succeeded, changing or returning the resource limit. A return value of -1 indicates that an error occurred, and an error code is stored in the global location .Va errno . .Sh ERRORS .Fn getrlimit and .Fn setrlimit will fail if: .Bl -tag -width Er .It Bq Er EFAULT The address specified for .Fa rlp is invalid. .It Bq Er EPERM The limit specified to .Fn setrlimit would have raised the maximum limit value, and the caller is not the super-user. .El .Sh SEE ALSO .Xr csh 1 , .Xr sh 1 , .Xr quotactl 2 , .Xr sigaction 2 , .Xr sigaltstack 2 , .Xr sysctl 3 .Sh HISTORY The .Fn getrlimit function call appeared in .Bx 4.2 .