1GETRLIMIT(3P) POSIX Programmer's Manual GETRLIMIT(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 getrlimit, setrlimit — control maximum resource consumption
13
15 #include <sys/resource.h>
16 int getrlimit(int resource, struct rlimit *rlp);
18 int setrlimit(int resource, const struct rlimit *rlp);
19
21 The getrlimit() function shall get, and the setrlimit() function shall
22 set, limits on the consumption of a variety of resources.
23 Each call to either getrlimit() or setrlimit() identifies a specific
25 resource to be operated upon as well as a resource limit. A resource
26 limit is represented by an rlimit structure. The rlim_cur member speci‐
27 fies the current or soft limit and the rlim_max member specifies the
28 maximum or hard limit. Soft limits may be changed by a process to any
29 value that is less than or equal to the hard limit. A process may
30 (irreversibly) lower its hard limit to any value that is greater than
31 or equal to the soft limit. Only a process with appropriate privileges
32 can raise a hard limit. Both hard and soft limits can be changed in a
33 single call to setrlimit() subject to the constraints described above.
34 The value RLIM_INFINITY, defined in <sys/resource.h>, shall be consid‐
36 ered to be larger than any other limit value. If a call to getrlimit()
37 returns RLIM_INFINITY for a resource, it means the implementation shall
38 not enforce limits on that resource. Specifying RLIM_INFINITY as any
39 resource limit value on a successful call to setrlimit() shall inhibit
40 enforcement of that resource limit.
41 The following resources are defined:
43 RLIMIT_CORE This is the maximum size of a core file, in bytes, that
45 may be created by a process. A limit of 0 shall prevent
46 the creation of a core file. If this limit is exceeded,
47 the writing of a core file shall terminate at this size.
48 RLIMIT_CPU This is the maximum amount of CPU time, in seconds, used
50 by a process. If this limit is exceeded, SIGXCPU shall
51 be generated for the process. If the process is catching
52 or ignoring SIGXCPU, or all threads belonging to that
53 process are blocking SIGXCPU, the behavior is unspeci‐
54 fied.
55 RLIMIT_DATA This is the maximum size of a data segment of the
57 process, in bytes. If this limit is exceeded, the mal‐
58 loc() function shall fail with errno set to [ENOMEM].
59 RLIMIT_FSIZE This is the maximum size of a file, in bytes, that may be
61 created by a process. If a write or truncate operation
62 would cause this limit to be exceeded, SIGXFSZ shall be
63 generated for the thread. If the thread is blocking, or
64 the process is catching or ignoring SIGXFSZ, continued
65 attempts to increase the size of a file from end-of-file
66 to beyond the limit shall fail with errno set to [EFBIG].
67 RLIMIT_NOFILE This is a number one greater than the maximum value that
69 the system may assign to a newly-created descriptor. If
70 this limit is exceeded, functions that allocate a file
71 descriptor shall fail with errno set to [EMFILE]. This
72 limit constrains the number of file descriptors that a
73 process may allocate.
74 RLIMIT_STACK This is the maximum size of the initial thread's stack,
76 in bytes. The implementation does not automatically grow
77 the stack beyond this limit. If this limit is exceeded,
78 SIGSEGV shall be generated for the thread. If the thread
79 is blocking SIGSEGV, or the process is ignoring or catch‐
80 ing SIGSEGV and has not made arrangements to use an
81 alternate stack, the disposition of SIGSEGV shall be set
82 to SIG_DFL before it is generated.
83 RLIMIT_AS This is the maximum size of total available memory of the
85 process, in bytes. If this limit is exceeded, the mal‐
86 loc() and mmap() functions shall fail with errno set to
87 [ENOMEM]. In addition, the automatic stack growth fails
88 with the effects outlined above.
89 When using the getrlimit() function, if a resource limit can be repre‐
91 sented correctly in an object of type rlim_t, then its representation
92 is returned; otherwise, if the value of the resource limit is equal to
93 that of the corresponding saved hard limit, the value returned shall be
94 RLIM_SAVED_MAX; otherwise, the value returned shall be RLIM_SAVED_CUR.
95 When using the setrlimit() function, if the requested new limit is
97 RLIM_INFINITY, the new limit shall be ``no limit''; otherwise, if the
98 requested new limit is RLIM_SAVED_MAX, the new limit shall be the cor‐
99 responding saved hard limit; otherwise, if the requested new limit is
100 RLIM_SAVED_CUR, the new limit shall be the corresponding saved soft
101 limit; otherwise, the new limit shall be the requested value. In addi‐
102 tion, if the corresponding saved limit can be represented correctly in
103 an object of type rlim_t then it shall be overwritten with the new
104 limit.
105 The result of setting a limit to RLIM_SAVED_MAX or RLIM_SAVED_CUR is
107 unspecified unless a previous call to getrlimit() returned that value
108 as the soft or hard limit for the corresponding resource limit.
109 The determination of whether a limit can be correctly represented in an
111 object of type rlim_t is implementation-defined. For example, some
112 implementations permit a limit whose value is greater than RLIM_INFIN‐
113 ITY and others do not.
114 The exec family of functions shall cause resource limits to be saved.
116
118 Upon successful completion, getrlimit() and setrlimit() shall return 0.
119 Otherwise, these functions shall return -1 and set errno to indicate
120 the error.
121
123 The getrlimit() and setrlimit() functions shall fail if:
124 EINVAL An invalid resource was specified; or in a setrlimit() call, the
126 new rlim_cur exceeds the new rlim_max.
127 EPERM The limit specified to setrlimit() would have raised the maximum
129 limit value, and the calling process does not have appropriate
130 privileges.
131 The setrlimit() function may fail if:
133 EINVAL The limit specified cannot be lowered because current usage is
135 already higher than the limit.
136 The following sections are informative.
138
140 None.
141
143 If a process attempts to set the hard limit or soft limit for
144 RLIMIT_NOFILE to less than the value of {_POSIX_OPEN_MAX} from <lim‐
145 its.h>, unexpected behavior may occur.
146 If a process attempts to set the hard limit or soft limit for
148 RLIMIT_NOFILE to less than the highest currently open file descriptor
149 +1, unexpected behavior may occur.
150
152 It should be noted that RLIMIT_STACK applies ``at least'' to the stack
153 of the initial thread in the process, and not to the sum of all the
154 stacks in the process, as that would be very limiting unless the value
155 is so big as to provide no value at all with a single thread.
156
158 None.
159
161 exec, fork(), malloc(), open(), sigaltstack(), sysconf(), ulimit()
162 The Base Definitions volume of POSIX.1‐2017, <stropts.h>,
164 <sys_resource.h>
165
167 Portions of this text are reprinted and reproduced in electronic form
168 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
169 table Operating System Interface (POSIX), The Open Group Base Specifi‐
170 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
171 Electrical and Electronics Engineers, Inc and The Open Group. In the
172 event of any discrepancy between this version and the original IEEE and
173 The Open Group Standard, the original IEEE and The Open Group Standard
174 is the referee document. The original Standard can be obtained online
175 at http://www.opengroup.org/unix/online.html .
176 Any typographical or formatting errors that appear in this page are
178 most likely to have been introduced during the conversion of the source
179 files to man page format. To report such errors, see https://www.ker‐
180 nel.org/doc/man-pages/reporting_bugs.html .
181IEEE/The Open Group 2017 GETRLIMIT(3P)