1.\" $NetBSD: getrlimit.2,v 1.7 1995/02/27 12:33:19 cgd 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 BSD 4 39.Sh NAME 40.Nm getrlimit , 41.Nm setrlimit 42.Nd control maximum system resource consumption 43.Sh SYNOPSIS 44.Fd #include <sys/types.h> 45.Fd #include <sys/time.h> 46.Fd #include <sys/resource.h> 47.Ft int 48.Fn getrlimit "int resource" "struct rlimit *rlp" 49.Ft int 50.Fn setrlimit "int resource" "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. 58.Pp 59The 60.Fa resource 61parameter is one of the following: 62.Bl -tag -width RLIMIT_FSIZEAA 63.It Li RLIMIT_CORE 64The largest size (in bytes) 65.Xr core 66file that may be created. 67.It Li RLIMIT_CPU 68The maximum amount of cpu time (in seconds) to be used by 69each process. 70.It Li RLIMIT_DATA 71The maximum size (in bytes) of the data segment for a process; 72this defines how far a program may extend its break with the 73.Xr sbrk 2 74system call. 75.It Li RLIMIT_FSIZE 76The largest size (in bytes) file that may be created. 77.It Li RLIMIT_MEMLOCK 78The maximum size (in bytes) which a process may lock into memory 79using the 80.Xr mlock 2 81function. 82.It Li RLIMIT_NOFILE 83The maximum number of open files for this process. 84.It Li RLIMIT_NPROC 85The maximum number of simultaneous processes for this user id. 86.It Li RLIMIT_RSS 87The maximum size (in bytes) to which a process's resident set size may 88grow. 89This imposes a limit on the amount of physical memory to be given to 90a process; if memory is tight, the system will prefer to take memory 91from processes that are exceeding their declared resident set size. 92.It Li RLIMIT_STACK 93The maximum size (in bytes) of the stack segment for a process; 94this defines how far a program's stack segment may be extended. 95Stack extension is performed automatically by the system. 96.El 97.Pp 98A resource limit is specified as a soft limit and a hard limit. When a 99soft limit is exceeded a process may receive a signal (for example, if 100the cpu time or file size is exceeded), but it will be allowed to 101continue execution until it reaches the hard limit (or modifies 102its resource limit). The 103.Em rlimit 104structure is used to specify the hard and soft limits on a resource, 105.Bd -literal -offset indent 106struct rlimit { 107 rlim_t rlim_cur; /* current (soft) limit */ 108 rlim_t rlim_max; /* hard limit */ 109}; 110.Ed 111.Pp 112Only the super-user may raise the maximum limits. Other users 113may only alter 114.Fa rlim_cur 115within the range from 0 to 116.Fa rlim_max 117or (irreversibly) lower 118.Fa rlim_max . 119.Pp 120An 121.Dq infinite 122value for a limit is defined as 123.Dv RLIM_INFINITY . 124.Pp 125Because this information is stored in the per-process information, 126this system call must be executed directly by the shell if it 127is to affect all future processes created by the shell; 128.Ic limit 129is thus a built-in command to 130.Xr csh 1 . 131.Pp 132The system refuses to extend the data or stack space when the limits 133would be exceeded in the normal way: a 134.Xr break 135call fails if the data space limit is reached. 136When the stack limit is reached, the process receives 137a segmentation fault 138.Pq Dv SIGSEGV ; 139if this signal is not 140caught by a handler using the signal stack, this signal 141will kill the process. 142.Pp 143A file I/O operation that would create a file larger that the process' 144soft limit will cause the write to fail and a signal 145.Dv SIGXFSZ 146to be 147generated; this normally terminates the process, but may be caught. When 148the soft cpu time limit is exceeded, a signal 149.Dv SIGXCPU 150is sent to the 151offending process. 152.Sh RETURN VALUES 153A 0 return value indicates that the call succeeded, changing 154or returning the resource limit. A return value of -1 indicates 155that an error occurred, and an error code is stored in the global 156location 157.Va errno . 158.Sh ERRORS 159.Fn Getrlimit 160and 161.Fn setrlimit 162will fail if: 163.Bl -tag -width Er 164.It Bq Er EFAULT 165The address specified for 166.Fa rlp 167is invalid. 168.It Bq Er EPERM 169The limit specified to 170.Fn setrlimit 171would have 172raised the maximum limit value, and the caller is not the super-user. 173.El 174.Sh SEE ALSO 175.Xr csh 1 , 176.Xr quota 2 , 177.Xr sigaction 2 , 178.Xr sigaltstack 2 , 179.Xr sysctl 3 180.Sh BUGS 181There should be 182.Ic limit 183and 184.Ic unlimit 185commands in 186.Xr sh 1 187as well as in 188.Xr csh . 189.Sh HISTORY 190The 191.Fn getrlimit 192function call appeared in 193.Bx 4.2 . 194