1.\" $NetBSD: getrlimit.2,v 1.15 1999/12/02 21:42:37 kleink Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt GETRLIMIT 2 38.Os 39.Sh NAME 40.Nm getrlimit , 41.Nm setrlimit 42.Nd control maximum system resource consumption 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.Fd #include <sys/types.h> 47.Fd #include <sys/time.h> 48.Fd #include <sys/resource.h> 49.Ft int 50.Fn getrlimit "int resource" "struct rlimit *rlp" 51.Ft int 52.Fn setrlimit "int resource" "const struct rlimit *rlp" 53.Sh DESCRIPTION 54Limits on the consumption of system resources by the current process 55and each process it creates may be obtained with the 56.Fn getrlimit 57call, and set with the 58.Fn setrlimit 59call. Resources of an arbitrary process can be obtained/changed using 60.Xr sysctl 3 . 61.. 62.Pp 63The 64.Fa resource 65parameter is one of the following: 66.Bl -tag -width RLIMIT_FSIZEAA 67.It Li RLIMIT_CORE 68The largest size (in bytes) 69.Pa core 70file that may be created. 71.It Li RLIMIT_CPU 72The maximum amount of cpu time (in seconds) to be used by 73each process. 74.It Li RLIMIT_DATA 75The maximum size (in bytes) of the data segment for a process; 76this defines how far a program may extend its break with the 77.Xr sbrk 2 78system call. 79.It Li RLIMIT_FSIZE 80The largest size (in bytes) file that may be created. 81.It Li RLIMIT_MEMLOCK 82The maximum size (in bytes) which a process may lock into memory 83using the 84.Xr mlock 2 85function. 86.It Li RLIMIT_NOFILE 87The maximum number of open files for this process. 88.It Li RLIMIT_NPROC 89The maximum number of simultaneous processes for this user id. 90.It Li RLIMIT_RSS 91The maximum size (in bytes) to which a process's resident set size may 92grow. 93This imposes a limit on the amount of physical memory to be given to 94a process; if memory is tight, the system will prefer to take memory 95from processes that are exceeding their declared resident set size. 96.It Li RLIMIT_STACK 97The maximum size (in bytes) of the stack segment for a process; 98this defines how far a program's stack segment may be extended. 99Stack extension is performed automatically by the system. 100.El 101.Pp 102A resource limit is specified as a soft limit and a hard limit. When a 103soft limit is exceeded a process may receive a signal (for example, if 104the cpu time or file size is exceeded), but it will be allowed to 105continue execution until it reaches the hard limit (or modifies 106its resource limit). The 107.Em rlimit 108structure is used to specify the hard and soft limits on a resource, 109.Bd -literal -offset indent 110struct rlimit { 111 rlim_t rlim_cur; /* current (soft) limit */ 112 rlim_t rlim_max; /* hard limit */ 113}; 114.Ed 115.Pp 116Only the super-user may raise the maximum limits. Other users 117may only alter 118.Fa rlim_cur 119within the range from 0 to 120.Fa rlim_max 121or (irreversibly) lower 122.Fa rlim_max . 123.Pp 124An 125.Dq infinite 126value for a limit is defined as 127.Dv RLIM_INFINITY . 128.Pp 129Because this information is stored in the per-process information, 130this system call must be executed directly by the shell if it 131is to affect all future processes created by the shell; 132.Ic limit 133is thus a built-in command to 134.Xr csh 1 . 135.Pp 136The system refuses to extend the data or stack space when the limits 137would be exceeded in the normal way: a 138.Xr brk 2 139call fails if the data space limit is reached. 140When the stack limit is reached, the process receives 141a segmentation fault 142.Pq Dv SIGSEGV ; 143if this signal is not 144caught by a handler using the signal stack, this signal 145will kill the process. 146.Pp 147A file I/O operation that would create a file larger that the process' 148soft limit will cause the write to fail and a signal 149.Dv SIGXFSZ 150to be 151generated; this normally terminates the process, but may be caught. When 152the soft cpu time limit is exceeded, a signal 153.Dv SIGXCPU 154is sent to the 155offending process. 156.Sh RETURN VALUES 157A 0 return value indicates that the call succeeded, changing 158or returning the resource limit. A return value of -1 indicates 159that an error occurred, and an error code is stored in the global 160location 161.Va errno . 162.Sh ERRORS 163.Fn getrlimit 164and 165.Fn setrlimit 166will fail if: 167.Bl -tag -width Er 168.It Bq Er EFAULT 169The address specified for 170.Fa rlp 171is invalid. 172.It Bq Er EPERM 173The limit specified to 174.Fn setrlimit 175would have 176raised the maximum limit value, and the caller is not the super-user. 177.El 178.Sh SEE ALSO 179.Xr csh 1 , 180.Xr sh 1 , 181.Xr quotactl 2 , 182.Xr sigaction 2 , 183.Xr sigaltstack 2 , 184.Xr sysctl 3 185.Sh HISTORY 186The 187.Fn getrlimit 188function call appeared in 189.Bx 4.2 . 190