1.\" $NetBSD: getrlimit.2,v 1.22 2002/10/01 18:10:44 wiz 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 November 23, 2001 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 \*[Lt]sys/resource.h\*[Gt] 47.Ft int 48.Fn getrlimit "int resource" "struct rlimit *rlp" 49.Ft int 50.Fn setrlimit "int resource" "const struct rlimit *rlp" 51.Sh DESCRIPTION 52Limits on the consumption of system resources by the current process 53and each process it creates may be obtained with the 54.Fn getrlimit 55call, and set with the 56.Fn setrlimit 57call. 58Resources of an arbitrary process can be obtained/changed using 59.Xr sysctl 3 . 60.. 61.Pp 62The 63.Fa resource 64parameter is one of the following: 65.Bl -tag -width RLIMIT_FSIZEAA 66.It Li RLIMIT_CORE 67The largest size (in bytes) 68.Pa core 69file that may be created. 70.It Li RLIMIT_CPU 71The maximum amount of cpu time (in seconds) to be used by 72each process. 73.It Li RLIMIT_DATA 74The maximum size (in bytes) of the data segment for a process; 75this defines how far a program may extend its break with the 76.Xr sbrk 2 77system call. 78.It Li RLIMIT_FSIZE 79The largest size (in bytes) file that may be created. 80.It Li RLIMIT_MEMLOCK 81The maximum size (in bytes) which a process may lock into memory 82using the 83.Xr mlock 2 84function. 85.It Li RLIMIT_NOFILE 86The maximum number of open files for this process. 87.It Li RLIMIT_NPROC 88The maximum number of simultaneous processes for this user id. 89.It Li RLIMIT_RSS 90The maximum size (in bytes) to which a process's resident set size may 91grow. 92This imposes a limit on the amount of physical memory to be given to 93a process; if memory is tight, the system will prefer to take memory 94from processes that are exceeding their declared resident set size. 95.It Li RLIMIT_STACK 96The maximum size (in bytes) of the stack segment for a process; 97this defines how far a program's stack segment may be extended. 98Stack extension is performed automatically by the system. 99.El 100.Pp 101A resource limit is specified as a soft limit and a hard limit. 102When a soft limit is exceeded a process may receive a signal (for example, 103if the cpu time or file size is exceeded), but it will be allowed to 104continue execution until it reaches the hard limit (or modifies 105its resource limit). 106The 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. 117Other users may 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. 132Thus, shells provide built-in commands to change the limits 133.Ic ( limit 134for 135.Xr csh 1 , 136or 137.Ic ulimit 138for 139.Xr sh 1 ) . 140.Pp 141The system refuses to extend the data or stack space when the limits 142would be exceeded in the normal way: a 143.Xr brk 2 144call fails if the data space limit is reached. 145When the stack limit is reached, the process receives 146a segmentation fault 147.Pq Dv SIGSEGV ; 148if this signal is not 149caught by a handler using the signal stack, this signal 150will kill the process. 151.Pp 152A file I/O operation that would create a file larger that the process' 153soft limit will cause the write to fail and a signal 154.Dv SIGXFSZ 155to be 156generated; this normally terminates the process, but may be caught. 157When the soft cpu time limit is exceeded, a signal 158.Dv SIGXCPU 159is sent to the 160offending process. 161.Sh RETURN VALUES 162A 0 return value indicates that the call succeeded, changing 163or returning the resource limit. 164Otherwise, -1 is returned and the global variable 165.Va errno 166is set to indicate the error. 167.Sh ERRORS 168The 169.Fn getrlimit 170and 171.Fn setrlimit 172will fail if: 173.Bl -tag -width Er 174.It Bq Er EFAULT 175The address specified for 176.Fa rlp 177is invalid. 178.It Bq Er EINVAL 179Specified 180.Fa resource 181was invalid. 182.It Bq Er EINVAL 183In the 184.Fn setrlimit 185call, the specified 186.Fa rlim_cur 187exceeds the specified 188.Fa rlim_max . 189.It Bq Er EPERM 190The limit specified to 191.Fn setrlimit 192would have 193raised the maximum limit value, and the caller is not the super-user. 194.El 195.Pp 196The 197.Fn setrlimit 198function may fail if: 199.Bl -tag -width Er 200.It Bq Er EINVAL 201The limit specified to 202.Fn setrlimit 203cannot be lowered, because current usage is already higher than the limit. 204.El 205.Sh SEE ALSO 206.Xr csh 1 , 207.Xr sh 1 , 208.Xr quotactl 2 , 209.Xr sigaction 2 , 210.Xr sigaltstack 2 , 211.Xr sysctl 3 212.\" Sh STANDARDS 213.\" With exception of 214.\" .Li RLIMIT_AS 215.\" (which is not currently supported), the 216.\" .Fn getrlimit 217.\" and 218.\" .Fn setrlimit 219.\" functions conform to 220.\" .St -susv2 . 221.Sh HISTORY 222The 223.Fn getrlimit 224function call appeared in 225.Bx 4.2 . 226