bsd/man/man2/getrlimit.2

   1 .\"     $NetBSD: getrlimit.2,v 1.8 1995/10/12 15:40:58 jtc 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" "const struct rlimit *rlp"
  51 .Sh DESCRIPTION
  52 Limits on the consumption of system resources by the current process
  53 and each process it creates may be obtained with the
  54 .Fn getrlimit
  55 call, and set with the
  56 .Fn setrlimit
  57 call.
  58 .Pp
  59 The
  60 .Fa resource
  61 parameter is one of the following:
  62 .Bl -tag -width RLIMIT_FSIZEAA
  63 .It Li RLIMIT_CORE
  64 The largest size (in bytes)
  65 .Xr core
  66 file that may be created.
  67 .It Li RLIMIT_CPU
  68 The maximum amount of cpu time (in seconds) to be used by
  69 each process.
  70 .It Li RLIMIT_DATA
  71 The maximum size (in bytes) of the data segment for a process;
  72 this defines how far a program may extend its break with the
  73 .Xr sbrk 2
  74 system call.
  75 .It Li RLIMIT_FSIZE
  76 The largest size (in bytes) file that may be created.
  77 .It Li RLIMIT_MEMLOCK
  78 The maximum size (in bytes) which a process may lock into memory
  79 using the
  80 .Xr mlock 2
  81 function.
  82 .It Li RLIMIT_NOFILE
  83 The maximum number of open files for this process.
  84 .It Li RLIMIT_NPROC
  85 The maximum number of simultaneous processes for this user id.
  86 .It Li RLIMIT_RSS
  87 The maximum size (in bytes) to which a process's resident set size may
  88 grow.
  89 This imposes a limit on the amount of physical memory to be given to
  90 a process; if memory is tight, the system will prefer to take memory
  91 from processes that are exceeding their declared resident set size.
  92 .It Li RLIMIT_STACK
  93 The maximum size (in bytes) of the stack segment for a process;
  94 this defines how far a program's stack segment may be extended.
  95 Stack extension is performed automatically by the system.
  96 .El
  97 .Pp
  98 A resource limit is specified as a soft limit and a hard limit.  When a
  99 soft limit is exceeded a process may receive a signal (for example, if
 100 the cpu time or file size is exceeded), but it will be allowed to
 101 continue execution until it reaches the hard limit (or modifies
 102 its resource limit).  The
 103 .Em rlimit
 104 structure is used to specify the hard and soft limits on a resource,
 105 .Bd -literal -offset indent
 106 struct rlimit {
 107         rlim_t  rlim_cur;       /* current (soft) limit */
 108         rlim_t  rlim_max;       /* hard limit */
 109 };
 110 .Ed
 111 .Pp
 112 Only the super-user may raise the maximum limits.  Other users
 113 may only alter
 114 .Fa rlim_cur
 115 within the range from 0 to
 116 .Fa rlim_max
 117 or (irreversibly) lower
 118 .Fa rlim_max .
 119 .Pp
 120 An
 121 .Dq infinite
 122 value for a limit is defined as
 123 .Dv RLIM_INFINITY .
 124 .Pp
 125 Because this information is stored in the per-process information,
 126 this system call must be executed directly by the shell if it
 127 is to affect all future processes created by the shell;
 128 .Ic limit
 129 is thus a built-in command to
 130 .Xr csh 1
 131 and
 132 .Ic ulimit
 133 is the
 134 .Xr sh 1
 135 equivalent.
 136 .Pp
 137 The system refuses to extend the data or stack space when the limits
 138 would be exceeded in the normal way: a
 139 .Xr break
 140 call fails if the data space limit is reached.
 141 When the stack limit is reached, the process receives
 142 a segmentation fault
 143 .Pq Dv SIGSEGV ;
 144 if this signal is not
 145 caught by a handler using the signal stack, this signal
 146 will kill the process.
 147 .Pp
 148 A file I/O operation that would create a file larger that the process'
 149 soft limit will cause the write to fail and a signal
 150 .Dv SIGXFSZ
 151 to be
 152 generated; this normally terminates the process, but may be caught.  When
 153 the soft cpu time limit is exceeded, a signal
 154 .Dv SIGXCPU
 155 is sent to the
 156 offending process.
 157 .Sh RETURN VALUES
 158 A 0 return value indicates that the call succeeded, changing
 159 or returning the resource limit.   A return value of -1 indicates
 160 that an error occurred, and an error code is stored in the global
 161 location
 162 .Va errno .
 163 .Sh ERRORS
 164 .Fn Getrlimit
 165 and
 166 .Fn setrlimit
 167 will fail if:
 168 .Bl -tag -width Er
 169 .It Bq Er EFAULT
 170 The address specified for
 171 .Fa rlp
 172 is invalid.
 173 .It Bq Er EPERM
 174 The limit specified to
 175 .Fn setrlimit
 176 would have
 177 raised the maximum limit value, and the caller is not the super-user.
 178 .El
 179 .Sh SEE ALSO
 180 .Xr csh 1 ,
 181 .Xr sh 1 ,
 182 .Xr quota 2 ,
 183 .Xr sigaction 2 ,
 184 .Xr sigaltstack 2 ,
 185 .Xr sysctl 3
 186 .Sh HISTORY
 187 The
 188 .Fn getrlimit
 189 function call appeared in
 190 .Bx 4.2 .