1.\" $OpenBSD: getrlimit.2,v 1.22 2013/07/17 05:42:11 schwarze Exp $ 2.\" $NetBSD: getrlimit.2,v 1.8 1995/10/12 15:40:58 jtc Exp $ 3.\" 4.\" Copyright (c) 1980, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: July 17 2013 $ 34.Dt GETRLIMIT 2 35.Os 36.Sh NAME 37.Nm getrlimit , 38.Nm setrlimit 39.Nd control maximum system resource consumption 40.Sh SYNOPSIS 41.Fd #include <sys/resource.h> 42.Ft int 43.Fn getrlimit "int resource" "struct rlimit *rlp" 44.Ft int 45.Fn setrlimit "int resource" "const struct rlimit *rlp" 46.Sh DESCRIPTION 47Limits on the consumption of system resources by the current process 48and each process it creates may be obtained with the 49.Fn getrlimit 50call, and set with the 51.Fn setrlimit 52call. 53.Pp 54The 55.Fa resource 56parameter is one of the following: 57.Bl -tag -width RLIMIT_FSIZEAA 58.It Li RLIMIT_CORE 59The largest size (in bytes) 60.Pa core 61file that may be created. 62.It Li RLIMIT_CPU 63The maximum amount of CPU time (in seconds) to be used by 64each process. 65.It Li RLIMIT_DATA 66The maximum size (in bytes) of the data segment for a process; 67this defines how far a program may extend its break with the 68.Xr sbrk 2 69system call. 70.It Li RLIMIT_FSIZE 71The largest size (in bytes) file that may be created. 72.It Li RLIMIT_MEMLOCK 73The maximum size (in bytes) which a process may lock into memory 74using the 75.Xr mlock 2 76function. 77.It Li RLIMIT_NOFILE 78The maximum number of open files for this process. 79.It Li RLIMIT_NPROC 80The maximum number of simultaneous processes for this user id. 81.It Li RLIMIT_RSS 82The maximum size (in bytes) to which a process's resident set size may 83grow. 84This imposes a limit on the amount of physical memory to be given to 85a process; if memory is tight, the system will prefer to take memory 86from processes that are exceeding their declared resident set size. 87.It Li RLIMIT_STACK 88The maximum size (in bytes) of the stack segment for a process, 89which defines how far a process's stack segment may be extended. 90Stack extension is performed automatically by the system, 91and is only used by the main thread of a process. 92.El 93.Pp 94A resource limit is specified as a soft limit and a hard limit. 95When a soft limit is exceeded a process may receive a signal (for example, 96if the CPU time or file size is exceeded), but it will be allowed to 97continue execution until it reaches the hard limit (or modifies 98its resource limit). 99The 100.Em rlimit 101structure is used to specify the hard and soft limits on a resource, 102.Bd -literal -offset indent 103struct rlimit { 104 rlim_t rlim_cur; /* current (soft) limit */ 105 rlim_t rlim_max; /* hard limit */ 106}; 107.Ed 108.Pp 109Only the superuser may raise the maximum limits. 110Other users may only alter 111.Fa rlim_cur 112within the range from 0 to 113.Fa rlim_max 114or (irreversibly) lower 115.Fa rlim_max . 116.Pp 117An 118.Dq infinite 119value for a limit is defined as 120.Dv RLIM_INFINITY . 121.Pp 122A value of 123.Dv RLIM_SAVED_CUR 124or 125.Dv RLIM_SAVED_MAX 126will be stored in 127.Fa rlim_cur 128or 129.Fa rlim_max 130respectively by 131.Fn getrlimit 132if the value for the current or maximum resource limit cannot be stored in an 133.Li rlim_t . 134The values 135.Dv RLIM_SAVED_CUR 136and 137.Dv RLIM_SAVED_MAX 138should not be used in a call to 139.Fn setrlimit 140unless they were returned by a previous call to 141.Fn getrlimit . 142.Pp 143Because this information is stored in the per-process information, 144this system call must be executed directly by the shell if it 145is to affect all future processes created by the shell; 146.Ic limit 147is thus a built-in command to 148.Xr csh 1 149and 150.Ic ulimit 151is the 152.Xr sh 1 153equivalent. 154.Pp 155The system refuses to extend the data or stack space when the limits 156would be exceeded in the normal way: a 157.Xr brk 2 158call fails if the data space limit is reached. 159When the stack limit is reached, the process receives 160a segmentation fault 161.Pq Dv SIGSEGV ; 162if this signal is not 163caught by a handler using the signal stack, this signal 164will kill the process. 165.Pp 166A file I/O operation that would create a file larger than the process' 167soft limit will cause the write to fail and a signal 168.Dv SIGXFSZ 169to be 170generated; this normally terminates the process, but may be caught. 171When the soft CPU time limit is exceeded, a signal 172.Dv SIGXCPU 173is sent to the 174offending process. 175.Sh RETURN VALUES 176A 0 return value indicates that the call succeeded, changing 177or returning the resource limit. 178A return value of \-1 indicates that an error occurred, and an error code 179is stored in the global variable 180.Va errno . 181.Sh ERRORS 182.Fn getrlimit 183and 184.Fn setrlimit 185will fail if: 186.Bl -tag -width Er 187.It Bq Er EFAULT 188The address specified for 189.Fa rlp 190is invalid. 191.It Bq Er EINVAL 192An unrecognized value for 193.Fa resource 194was specified. 195.El 196.Pp 197In addition, 198.Fn setrlimit 199may return the following errors: 200.Bl -tag -width Er 201.It Bq Er EINVAL 202The new 203.Fa rlim_cur 204is greater than the new 205.Fa rlim_max . 206.It Bq Er EPERM 207The new 208.Fa rlim_max 209is greater than the current maximum limit value, 210and the caller is not the superuser. 211.El 212.Sh SEE ALSO 213.Xr csh 1 , 214.Xr sh 1 , 215.Xr quotactl 2 , 216.Xr sigaction 2 , 217.Xr sigaltstack 2 , 218.Xr sysctl 3 219.Sh STANDARDS 220The 221.Fn getrlimit 222and 223.Fn setrlimit 224functions conform to 225.St -p1003.1-2008 . 226.Pp 227The 228.Dv RLIMIT_MEMLOCK , 229.Dv RLIMIT_NPROC , 230and 231.Dv RLIMIT_RSS 232resources are non-standard extensions. 233.Sh HISTORY 234The 235.Fn getrlimit 236and 237.Fn setrlimit 238system calls first appeared in 239.Bx 4.1c . 240.Sh BUGS 241The 242.Dv RLIMIT_AS 243resource is missing. 244