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28 .\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93
30 .Dd September 30, 2016
36 .Nd control maximum system resource consumption
44 .Fn getrlimit "int resource" "struct rlimit *rlp"
46 .Fn setrlimit "int resource" "const struct rlimit *rlp"
48 Limits on the consumption of system resources by the current process
49 and each process it creates may be obtained with the
51 system call, and set with the
57 argument is one of the following:
58 .Bl -tag -width RLIMIT_FSIZEAA
60 The maximum amount (in bytes) of virtual memory the process is
63 The largest size (in bytes)
65 file that may be created.
67 The maximum amount of cpu time (in seconds) to be used by
70 The maximum size (in bytes) of the data segment for a process;
71 this defines how far a program may extend its break with the
75 The largest size (in bytes) file that may be created.
77 The maximum number of kqueues this user id is allowed to create.
79 The maximum size (in bytes) which a process may lock into memory
84 The maximum number of open files for this process.
86 The maximum number of simultaneous processes for this user id.
88 The maximum number of pseudo-terminals this user id is allowed to create.
90 When there is memory pressure and swap is available, prioritize eviction of
91 a process' resident pages beyond this amount (in bytes).
92 When memory is not under pressure, this rlimit is effectively ignored.
93 Even when there is memory pressure, the amount of available swap space and some
97 .Xr vm.swap_idle_enabled
98 can affect what happens to processes that have exceeded this size.
100 Processes that exceed their set
102 are not signalled or halted.
103 The limit is merely a hint to the VM daemon to prefer to deactivate pages from
104 processes that have exceeded their set
107 The maximum size (in bytes) of socket buffer usage for this user.
108 This limits the amount of network memory, and hence the amount of
109 mbufs, that this user may hold at any time.
111 The maximum size (in bytes) of the stack segment for a process;
112 this defines how far a program's stack segment may be extended.
113 Stack extension is performed automatically by the system.
115 The maximum size (in bytes) of the swap space that may be reserved or
116 used by all of this user id's processes.
117 This limit is enforced only if bit 1 of the
122 for a complete description of this sysctl.
128 A resource limit is specified as a soft limit and a hard limit.
129 When a soft limit is exceeded, a process might or might not receive a signal.
130 For example, signals are generated when the cpu time or file size is exceeded,
131 but not if the address space or RSS limit is exceeded.
132 A program that exceeds the soft limit is allowed to continue execution until it
133 reaches the hard limit, or modifies its own resource limit.
134 Even reaching the hard limit does not necessarily halt a process.
135 For example, if the RSS hard limit is exceeded, nothing happens.
139 structure is used to specify the hard and soft limits on a resource.
140 .Bd -literal -offset indent
142 rlim_t rlim_cur; /* current (soft) limit */
143 rlim_t rlim_max; /* maximum value for rlim_cur */
147 Only the super-user may raise the maximum limits.
151 within the range from 0 to
153 or (irreversibly) lower
158 value for a limit is defined as
161 Because this information is stored in the per-process information,
162 this system call must be executed directly by the shell if it
163 is to affect all future processes created by the shell;
165 is thus a built-in command to
168 The system refuses to extend the data or stack space when the limits
169 would be exceeded in the normal way: a
171 function fails if the data space limit is reached.
172 When the stack limit is reached, the process receives
175 if this signal is not
176 caught by a handler using the signal stack, this signal
177 will kill the process.
179 A file I/O operation that would create a file larger that the process'
180 soft limit will cause the write to fail and a signal
183 generated; this normally terminates the process, but may be caught.
185 the soft cpu time limit is exceeded, a
187 signal is sent to the
190 When most operations would allocate more virtual memory than allowed by the
193 the operation fails with
195 and no signal is raised.
196 A notable exception is stack extension, described above.
197 If stack extension would allocate more virtual memory than allowed by the soft
202 signal will be delivered.
203 The caller is free to raise the soft address space limit up to the hard limit
204 and retry the allocation.
216 The address specified for
220 The limit specified to
223 raised the maximum limit value, and the caller is not the super-user.
236 system call appeared in