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28 .\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93
37 .Nd control maximum system resource consumption
45 .Fn getrlimit "int resource" "struct rlimit *rlp"
47 .Fn setrlimit "int resource" "const struct rlimit *rlp"
49 Limits on the consumption of system resources by the current process
50 and each process it creates may be obtained with the
52 system call, and set with the
58 argument is one of the following:
59 .Bl -tag -width RLIMIT_FSIZEAA
61 The maximum amount (in bytes) of virtual memory the process is
64 The largest size (in bytes)
66 file that may be created.
68 The maximum amount of cpu time (in seconds) to be used by
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
76 The largest size (in bytes) file that may be created.
78 The maximum number of kqueues this user id is allowed to create.
80 The maximum size (in bytes) which a process may lock into memory
85 The maximum number of open files for this process.
87 The maximum number of simultaneous processes for this user id.
89 The maximum number of pseudo-terminals this user id is allowed to create.
91 When there is memory pressure and swap is available, prioritize eviction of
92 a process' resident pages beyond this amount (in bytes).
93 When memory is not under pressure, this rlimit is effectively ignored.
94 Even when there is memory pressure, the amount of available swap space and some
98 .Xr vm.swap_idle_enabled
99 can affect what happens to processes that have exceeded this size.
101 Processes that exceed their set
103 are not signalled or halted.
104 The limit is merely a hint to the VM daemon to prefer to deactivate pages from
105 processes that have exceeded their set
108 The maximum size (in bytes) of socket buffer usage for this user.
109 This limits the amount of network memory, and hence the amount of
110 mbufs, that this user may hold at any time.
112 The maximum size (in bytes) of the stack segment for a process;
113 this defines how far a program's stack segment may be extended.
114 Stack extension is performed automatically by the system.
116 The maximum size (in bytes) of the swap space that may be reserved or
117 used by all of this user id's processes.
118 This limit is enforced only if bit 1 of the
123 for a complete description of this sysctl.
129 A resource limit is specified as a soft limit and a hard limit.
130 When a soft limit is exceeded, a process might or might not receive a signal.
131 For example, signals are generated when the cpu time or file size is exceeded,
132 but not if the address space or RSS limit is exceeded.
133 A program that exceeds the soft limit is allowed to continue execution until it
134 reaches the hard limit, or modifies its own resource limit.
135 Even reaching the hard limit does not necessarily halt a process.
136 For example, if the RSS hard limit is exceeded, nothing happens.
140 structure is used to specify the hard and soft limits on a resource,
141 .Bd -literal -offset indent
143 rlim_t rlim_cur; /* current (soft) limit */
144 rlim_t rlim_max; /* maximum value for rlim_cur */
148 Only the super-user may raise the maximum limits.
152 within the range from 0 to
154 or (irreversibly) lower
159 value for a limit is defined as
162 Because this information is stored in the per-process information,
163 this system call must be executed directly by the shell if it
164 is to affect all future processes created by the shell;
166 is thus a built-in command to
169 The system refuses to extend the data or stack space when the limits
170 would be exceeded in the normal way: a
172 function fails if the data space limit is reached.
173 When the stack limit is reached, the process receives
176 if this signal is not
177 caught by a handler using the signal stack, this signal
178 will kill the process.
180 A file I/O operation that would create a file larger that the process'
181 soft limit will cause the write to fail and a signal
184 generated; this normally terminates the process, but may be caught.
186 the soft cpu time limit is exceeded, a signal
191 When most operations would allocate more virtual memory than allowed by the
194 the operation fails with
196 and no signal is raised.
197 A notable exception is stack extension, described above.
198 If stack extension would allocate more virtual memory than allowed by the soft
201 the signal SIGSEGV will be delivered.
202 The caller is free to raise the soft address space limit up to the hard limit
203 and retry the allocation.
215 The address specified for
219 The limit specified to
222 raised the maximum limit value, and the caller is not the super-user.
235 system call appeared in