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1.1 root 1: .\" Copyright (c) 1980 Regents of the University of California.
2: .\" All rights reserved. The Berkeley software License Agreement
3: .\" specifies the terms and conditions for redistribution.
4: .\"
5: .\" @(#)getrlimit.2 6.4 (Berkeley) 4/3/87
6: .\"
7: .TH GETRLIMIT 2 "April 3, 1987"
8: .UC 4
9: .SH NAME
10: getrlimit, setrlimit \- control maximum system resource consumption
11: .SH SYNOPSIS
12: .ft B
13: .nf
14: #include <sys/time.h>
15: #include <sys/resource.h>
16: .PP
17: .ft B
18: getrlimit(resource, rlp)
19: int resource;
20: struct rlimit *rlp;
21: .PP
22: .ft B
23: setrlimit(resource, rlp)
24: int resource;
25: struct rlimit *rlp;
26: .fi
27: .ft R
28: .SH DESCRIPTION
29: Limits on the consumption of system resources by the current process
30: and each process it creates may be obtained with the
31: .I getrlimit
32: call, and set with the
33: .I setrlimit
34: call.
35: .PP
36: The
37: .I resource
38: parameter is one of the following:
39: .TP 17
40: RLIMIT_CPU
41: the maximum amount of cpu time (in seconds) to be used by
42: each process.
43: .TP 17
44: RLIMIT_FSIZE
45: the largest size, in bytes, of any single file that may be created.
46: .TP 17
47: RLIMIT_DATA
48: the maximum size, in bytes, of the data segment for a process;
49: this defines how far a program may extend its break with the
50: .IR sbrk (2)
51: system call.
52: .TP 17
53: RLIMIT_STACK
54: the maximum size, in bytes, of the stack segment for a process;
55: this defines how far a program's stack segment may be extended.
56: Stack extension is performed automatically by the system.
57: .TP 17
58: RLIMIT_CORE
59: the largest size, in bytes, of a
60: .I core
61: file that may be created.
62: .TP 17
63: RLIMIT_RSS
64: the maximum size, in bytes, to which a process's resident set size may
65: grow. This imposes a limit on the amount of physical memory
66: to be given to a process; if memory is tight, the system will
67: prefer to take memory from processes that are exceeding their
68: declared resident set size.
69: .PP
70: A resource limit is specified as a soft limit and a hard limit. When a
71: soft limit is exceeded a process may receive a signal (for example, if
72: the cpu time or file size is exceeded), but it will be allowed to
73: continue execution until it reaches the hard limit (or modifies
74: its resource limit). The
75: .I rlimit
76: structure is used to specify the hard and soft limits on a resource,
77: .PP
78: .nf
79: .RS
80: .DT
81: struct rlimit {
82: int rlim_cur; /* current (soft) limit */
83: int rlim_max; /* hard limit */
84: };
85: .RE
86: .fi
87: .PP
88: Only the super-user may raise the maximum limits. Other users
89: may only alter
90: .I rlim_cur
91: within the range from 0 to
92: .I rlim_max
93: or (irreversibly) lower
94: .IR rlim_max .
95: .PP
96: An \*(lqinfinite\*(rq value for a limit is defined as RLIM_INFINITY
97: (0x7\&f\&f\&f\&f\&f\&f\&f).
98: .PP
99: Because this information is stored in the per-process information,
100: this system call must be executed directly by the shell if it
101: is to affect all future processes created by the shell;
102: .I limit
103: is thus a built-in command to
104: .IR csh (1).
105: .PP
106: The system refuses to extend the data or stack space when the limits
107: would be exceeded in the normal way: a
108: .I break
109: call fails if the data space limit is reached.
110: When the stack limit is reached, the process receives
111: a segmentation fault (SIGSEGV); if this signal is not
112: caught by a handler using the signal stack, this signal
113: will kill the process.
114: .PP
115: A file I/O operation that would create a file larger that the process'
116: soft limit will cause the write to fail and a signal SIGXFSZ to be
117: generated; this normally terminates the process, but may be caught. When
118: the soft cpu time limit is exceeded, a signal SIGXCPU is sent to the
119: offending process.
120: .SH "RETURN VALUE
121: A 0 return value indicates that the call succeeded, changing
122: or returning the resource limit. A return value of \-1 indicates
123: that an error occurred, and an error code is stored in the global
124: location \fIerrno\fP.
125: .SH "ERRORS
126: The possible errors are:
127: .TP 15
128: [EFAULT]
129: The address specified for \fIrlp\fP is invalid.
130: .TP 15
131: [EPERM] The limit specified to \fIsetrlimit\fP would have
132: raised the maximum limit value, and the caller is not the super-user.
133: .SH SEE ALSO
134: csh(1), quota(2), sigvec(2), sigstack(2)
135: .SH BUGS
136: There should be
137: .I limit
138: and
139: .I unlimit
140: commands in
141: .IR sh (1)
142: as well as in
143: .IR csh.
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