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33 .Nd get configurable system variables
39 .Fn sysconf "int name"
41 This interface is defined by
43 A far more complete interface is available using
48 function provides a method for applications to determine the current
49 value of a configurable system limit or option variable.
52 argument specifies the system variable to be queried.
53 Symbolic constants for each name value are found in the include file
55 Shell programmers who need access to these parameters should use the
59 The available values are as follows:
62 The maximum bytes of argument to
65 The maximum number of simultaneous processes per user id.
67 The frequency of the statistics clock in ticks per second.
69 The maximum number of elements in the I/O vector used by
75 .It Li _SC_NGROUPS_MAX
76 The maximum number of supplemental groups.
77 .It Li _SC_NPROCESSORS_CONF
78 The number of processors configured.
79 .It Li _SC_NPROCESSORS_ONLN
80 The number of processors currently online.
82 One more than the maximum value the system may assign to a new file descriptor.
84 The size of a system page in bytes.
89 The minimum maximum number of streams that a process may have open
92 The minimum maximum number of types supported for the name of a
94 .It Li _SC_JOB_CONTROL
95 Return 1 if job control is available on this system, otherwise \-1.
97 Returns 1 if saved set-group and saved set-user ID is available,
102 with which the system
104 .It Li _SC_BC_BASE_MAX
105 The maximum ibase/obase values in the
108 .It Li _SC_BC_DIM_MAX
109 The maximum array size in the
112 .It Li _SC_BC_SCALE_MAX
113 The maximum scale value in the
116 .It Li _SC_BC_STRING_MAX
117 The maximum string length in the
120 .It Li _SC_COLL_WEIGHTS_MAX
121 The maximum number of weights that can be assigned to any entry of
122 the LC_COLLATE order keyword in the locale definition file.
123 .It Li _SC_EXPR_NEST_MAX
124 The maximum number of expressions that can be nested within
129 The maximum length in bytes of a text-processing utility's input
131 .It Li _SC_RE_DUP_MAX
132 The maximum number of repeated occurrences of a regular expression
133 permitted when using interval notation.
137 with which the system attempts to comply.
139 Return 1 if the system's C-language development facilities support the
140 C-Language Bindings Option, otherwise \-1.
142 Return 1 if the system supports the C-Language Development Utilities Option,
144 .It Li _SC_2_CHAR_TERM
145 Return 1 if the system supports at least one terminal type capable of
146 all operations described in
149 .It Li _SC_2_FORT_DEV
150 Return 1 if the system supports the FORTRAN Development Utilities Option,
152 .It Li _SC_2_FORT_RUN
153 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
155 .It Li _SC_2_LOCALEDEF
156 Return 1 if the system supports the creation of locales, otherwise \-1.
158 Return 1 if the system supports the Software Development Utilities Option,
161 Return 1 if the system supports the User Portability Utilities Option,
163 .It Li _SC_AIO_LISTIO_MAX
164 Maximum number of I/O operations in a single list I/O call supported.
166 Maximum number of outstanding asynchronous I/O operations supported.
167 .It Li _SC_AIO_PRIO_DELTA_MAX
168 The maximum amount by which a process can decrease its asynchronous I/O
169 priority level from its own scheduling priority.
170 .It Li _SC_DELAYTIMER_MAX
171 Maximum number of timer expiration overruns.
172 .It Li _SC_MQ_OPEN_MAX
173 The maximum number of open message queue descriptors a process may hold.
175 Maximum number of realtime signals reserved for application use.
176 .It Li _SC_SEM_NSEMS_MAX
177 Maximum number of semaphores that a process may have.
178 .It Li _SC_SEM_VALUE_MAX
179 The maximum value a semaphore may have.
180 .It Li _SC_SIGQUEUE_MAX
181 Maximum number of queued signals that a process may send and have pending at
182 the receiver(s) at any time.
184 Maximum number of timers per process supported.
185 .It Li _SC_GETGR_R_SIZE_MAX
186 Suggested initial value for the size of the group entry buffer.
187 .It Li _SC_GETPW_R_SIZE_MAX
188 Suggested initial value for the size of the password entry buffer.
189 .It Li _SC_HOST_NAME_MAX
190 Maximum length of a host name (not including the terminating null) as
194 .It Li _SC_LOGIN_NAME_MAX
195 Maximum length of a login name.
196 .It Li _SC_THREAD_STACK_MIN
197 Minimum size in bytes of thread stack storage.
198 .It Li _SC_THREAD_THREADS_MAX
199 Maximum number of threads that can be created per process.
200 .It Li _SC_TTY_NAME_MAX
201 Maximum length of terminal device name.
202 .It Li _SC_SYMLOOP_MAX
203 Maximum number of symbolic links that can be reliably traversed in the
204 resolution of a pathname in the absence of a loop.
205 .It Li _SC_ATEXIT_MAX
206 Maximum number of functions that may be registered with
208 .It Li _SC_XOPEN_VERSION
209 An integer value greater than or equal to 4,
210 indicating the version of the X/Open Portability Guide to which this
212 .It Li _SC_XOPEN_XCU_VERSION
213 An integer value indicating the version of the XCU Specification to which
214 this system conforms.
217 These values also exist, but may not be standard:
219 .It Li _SC_CPUSET_SIZE
220 Size of the kernel cpuset.
221 .It Li _SC_PHYS_PAGES
222 The number of pages of physical memory.
223 Note that it is possible that the product of this value and the value of
227 in some configurations on a 32bit machine.
232 is not successful, \-1 is returned and
234 is set appropriately.
235 Otherwise, if the variable is associated with functionality that is not
236 supported, \-1 is returned and
239 Otherwise, the current variable value is returned.
243 function may fail and set
245 for any of the errors specified for the library function
247 In addition, the following error may be reported:
260 Except for the fact that values returned by
262 may change over the lifetime of the calling process,
263 this function conforms to
268 function first appeared in
271 The value for _SC_STREAM_MAX is a minimum maximum, and required to be
272 the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
273 small and misleading number.