1.\" Copyright (c) 1996 David Nugent <davidn@blaze.net.au> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, is permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice immediately at the beginning of the file, without modification, 9.\" this list of conditions, and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. This work was done expressly for inclusion into FreeBSD. Other use 14.\" is permitted provided this notation is included. 15.\" 4. Absolutely no warranty of function or purpose is made by the author 16.\" David Nugent. 17.\" 5. Modifications may be freely made to this file providing the above 18.\" conditions are met. 19.\" 20.\" $FreeBSD$ 21.\" 22.Dd January 15, 1996 23.Dt LIMITS 1 24.Os 25.Sh NAME 26.Nm limits 27.Nd set or display process resource limits 28.Sh SYNOPSIS 29.Nm 30.Op Fl C Ar class 31.Op Fl SHB 32.Op Fl ea 33.Op Fl cdflmnstu Op val 34.Nm 35.Op Fl C Ar class 36.Op Fl SHB 37.Op Fl cdflmnstu Op val 38.Op Fl E 39.Op Ar name Ns = Ns Ar value ... 40.Op Ar command 41.Nm 42.Op Fl U Ar user 43.Op Fl SHB 44.Op Fl ea 45.Op Fl cdflmnstu Op val 46.Nm 47.Op Fl U Ar user 48.Op Fl SHB 49.Op Fl cdflmnstu Op val 50.Op Fl E 51.Op Ar name Ns = Ns Ar value ... 52.Op Ar command 53.Sh DESCRIPTION 54The 55.Nm 56utility either prints or sets kernel resource limits, and may optionally set 57environment variables like 58.Xr env 1 59and run a program with the selected resources. 60Three uses of the 61.Nm 62command are possible: 63.Pp 64.Bl -tag -width indent 65.It Xo 66.Nm 67.Op Ar limitflags 68.Op Ar name Ns = Ns Ar value 69.Ar command 70.Xc 71This usage sets limits according to 72.Ar limitflags , 73optionally sets environment variables given as 74.Ar name Ns = Ns Ar value 75pairs, and then runs the specified command. 76.It Xo 77.Nm 78.Op Ar limitflags 79.Xc 80This usage determines values of resource settings according to 81.Ar limitflags , 82does not attempt to set them and outputs these values to 83standard output. 84By default, this will output the current kernel resource settings 85active for the calling process. 86Using the 87.Fl C Ar class 88or 89.Fl U Ar user 90flags, you may also display the current resource settings modified 91by the appropriate login class resource limit entries from 92the 93.Xr login.conf 5 94login capabilities database. 95.It Xo 96.Nm 97.Fl e Op Ar limitflags 98.Xc 99This usage determines values of resource settings according to 100.Ar limitflags , 101but does not set them itself. 102Like the previous usage it outputs these values to standard 103output, except that it will emit them in 104.Em eval 105format, suitable for the calling shell. 106The calling shell is determined by examining the entries in the 107.Pa /proc 108filesystem for the parent process. 109If the shell is known (i.e. it is one of sh, csh, bash, tcsh, ksh, 110pdksh or rc), 111.Nm 112emits 'limit' or 'ulimit' commands in the format understood by 113that shell. 114If the name of the shell cannot be determined, then the 'ulimit' 115format used by 116.Xr sh 1 117is used. 118.Pp 119This is very useful for setting limits used by scripts, or prior 120launching of daemons and other background tasks with specific 121resource limit settings, and provides the benefit of allowing 122global configuration of maximum resource usage by maintaining a 123central database of settings in the login class database. 124.Pp 125Within a shell script, 126.Nm 127will normally be used with eval within backticks as follows: 128.Pp 129.Dl eval `limits -e -C daemon` 130.Pp 131which causes the output of 132.Nm 133to be evaluated and set by the current shell. 134.El 135.Pp 136The value of limitflags specified in the above contains one or more of the 137following options: 138.Pp 139.Bl -tag -width "-d [limit]" 140.It Fl C Ar class 141Use current resource values, modified by the resource entries applicable 142for the login class "class". 143.It Fl U Ar user 144Use current resource values, modified by the resource entries applicable 145to the login class which "user" belongs to. 146If the user does not belong to a class, then the resource capabilities 147for the "default" class are used, if it exists, or the "root" class if 148the user is a superuser account. 149.It Fl S 150Select display or setting of "soft" (or current) resource limits. 151If specific limits settings follow this switch, only soft limits are 152affected unless overridden later with either the 153.Fl H 154or 155.Fl B 156flags. 157.It Fl H 158Select display or setting of "hard" (or maximum) resource limits. 159If specific limits settings follow this switch, only hard limits are 160affected until overridden later with either the 161.Fl S 162or 163.Fl B 164flags. 165.It Fl B 166Select display or setting of both "soft" (current) or "hard" (maximum) 167resource limits. 168If specific limits settings follow this switch, both soft and hard 169limits are affected until overridden later with either the 170.Fl S 171or 172.Fl H 173flags. 174.Fl e 175Select "eval mode" formatting for output. 176This is valid only on display mode and cannot be used when running a 177command. 178The exact syntax used for output depends upon the type of shell from 179which 180.Nm 181is invoked. 182.It Fl b Op Ar limit 183Selects or sets the 184.Em sbsize 185resource limit. 186.It Fl c Op Ar limit 187Select or set (if 'limit' is specified) the 188.Em coredumpsize 189resource limit. 190A value of 0 disables core dumps. 191.It Fl d Op Ar limit 192Select or set (if 'limit' is specified) the 193.Em datasize 194resource limit. 195.It Fl f Op Ar limit 196Select or set the 197.Em filesize 198resource limit. 199.It Fl l Op Ar limit 200Select or set the 201.Em memorylocked 202resource limit. 203.It Fl m Op Ar limit 204Select or set the 205.Em memoryuse 206size limit. 207.It Fl n Op Ar limit 208Select or set the 209.Em openfiles 210resource limit. The system-wide limit on the maximum number of 211open files per process can be viewed using the 'sysctl kern.maxfilesperproc' 212command. The total number of simultaneously open files in the entire 213system is limited to the value displayed by the 'sysctl kern.maxfiles' 214command. 215.It Fl s Op Ar limit 216Select or set the 217.Em stacksize 218resource limit. 219.It Fl t Op Ar limit 220Select or set the 221.Em cputime 222resource limit. 223.It Fl u Op Ar limit 224Select or set the 225.Em maxproc 226resource limit. The system-wide limit on the maximum number of processes 227allowed per UID can be viewed using the 'sysctl kern.maxprocperuid' command. 228The maximum number of processes that can be running simultaneously 229in the entire system is limited to the value given by 230the 'sysctl kern.maxproc' command. 231.Pp 232Valid values for 233.Ar limit 234in the above set of flags consist of either the 235string 236.Em infinity , 237.Em inf , 238.Em unlimited 239or 240.Em unlimit 241for an infinite (or kernel-defined maximum) 242limit, or a numeric value maybe followed by a suffix. 243Values which relate to size default to a value in bytes, or one of the 244following suffixes may be used as a multiplier: 245.Pp 246.Bl -tag -offset indent -width "xxxx" -compact 247.It b 248512 byte blocks. 249.It k 250kilobytes (1024 bytes). 251.It m 252megabytes (1024*1024 bytes). 253.It g 254gigabytes. 255.It t 256terabytes. 257.El 258.Pp 259The 260.Em cputime 261resource defaults to a number of seconds, but a multiplier may be 262used, and as with size values, multiple values separated by a valid 263suffix are added together: 264.Bl -tag -offset indent -width "xxxx" -compact 265.It s 266seconds. 267.It m 268minutes. 269.It h 270hours. 271.It d 272days. 273.It w 274weeks. 275.It y 276365 day years. 277.El 278.Pp 279.It Fl E 280The option 281.Sq Fl E 282causes 283.Nm 284to completely ignore the environment it inherits. 285.It Fl a 286This option forces all resource settings to be displayed even if 287other specific resource settings have been specified. 288For example, if you wish to disable core dumps when starting up 289the usenet news system, but wish to set all other resource settings 290as well that apply to the 'news' account, you might use: 291.Pp 292.Dl eval `limits -U news -aBec 0` 293.Pp 294As with the 295.Xr setrlimit 2 296call, only the superuser may raise process "hard" resource limits. 297Non-root users may, however, lower them or change "soft" resource limits 298within to any value below the hard limit. 299When invoked to execute a program, the failure of 300.Nm 301to raise a hard limit is considered a fatal error. 302.El 303.Sh DIAGNOSTICS 304The 305.Nm 306utility 307exits with EXIT_FAILURE if usage is incorrect in any way; i.e. an invalid 308option, or set/display options are selected in the same invocation, 309.Fl e 310is used when running a program, etc. 311When run in display or eval mode, 312.Nm 313exits with a status of EXIT_SUCCESS. 314When run in command mode and execution of the command succeeds, the exit status 315will be whatever the executed program returns. 316.Sh SEE ALSO 317.Xr csh 1 , 318.Xr env 1 , 319.Xr limit 1 , 320.Xr sh 1 , 321.Xr getrlimit 2 , 322.Xr setrlimit 2 , 323.Xr login_cap 3 , 324.Xr login.conf 5 , 325.Xr sysctl 8 326.Sh BUGS 327The 328.Nm 329utility does not handle commands with equal (``='') signs in their 330names, for obvious reasons. 331.Pp 332When eval output is selected, the 333.Pa /proc 334filesystem must be installed 335and mounted for the shell to be correctly determined, and therefore 336output syntax correct for the running shell. 337The default output is valid for 338.Xr sh 1 , 339so this means that any 340usage of 341.Nm 342in eval mode prior mounting 343.Pa /proc 344may only occur in standard bourne 345shell scripts. 346.Pp 347The 348.Nm 349utility makes no effort to ensure that resource settings emitted or displayed 350are valid and settable by the current user. 351Only a superuser account may raise hard limits, and when doing so 352the 353.Fx 354kernel will silently lower limits to values less than 355specified if the values given are too high. 356