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28 .\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94
36 .Nd get configurable system variables
42 .Fn sysconf "int name"
44 This interface is defined by
46 A far more complete interface is available using
51 function provides a method for applications to determine the current
52 value of a configurable system limit or option variable.
55 argument specifies the system variable to be queried.
56 Symbolic constants for each name value are found in the include file
58 Shell programmers who need access to these parameters should use the
62 The available values are as follows:
65 The maximum bytes of argument to
68 The maximum number of simultaneous processes per user id.
70 The frequency of the statistics clock in ticks per second.
72 The maximum number of elements in the I/O vector used by
78 .It Li _SC_NGROUPS_MAX
79 The maximum number of supplemental groups.
80 .It Li _SC_NPROCESSORS_CONF
81 The number of processors configured.
82 .It Li _SC_NPROCESSORS_ONLN
83 The number of processors currently online.
85 One more than the maximum value the system may assign to a new file descriptor.
87 The size of a system page in bytes.
92 The minimum maximum number of streams that a process may have open
95 The minimum maximum number of types supported for the name of a
97 .It Li _SC_JOB_CONTROL
98 Return 1 if job control is available on this system, otherwise \-1.
100 Returns 1 if saved set-group and saved set-user ID is available,
105 with which the system
107 .It Li _SC_BC_BASE_MAX
108 The maximum ibase/obase values in the
111 .It Li _SC_BC_DIM_MAX
112 The maximum array size in the
115 .It Li _SC_BC_SCALE_MAX
116 The maximum scale value in the
119 .It Li _SC_BC_STRING_MAX
120 The maximum string length in the
123 .It Li _SC_COLL_WEIGHTS_MAX
124 The maximum number of weights that can be assigned to any entry of
125 the LC_COLLATE order keyword in the locale definition file.
126 .It Li _SC_EXPR_NEST_MAX
127 The maximum number of expressions that can be nested within
132 The maximum length in bytes of a text-processing utility's input
134 .It Li _SC_RE_DUP_MAX
135 The maximum number of repeated occurrences of a regular expression
136 permitted when using interval notation.
140 with which the system attempts to comply.
142 Return 1 if the system's C-language development facilities support the
143 C-Language Bindings Option, otherwise \-1.
145 Return 1 if the system supports the C-Language Development Utilities Option,
147 .It Li _SC_2_CHAR_TERM
148 Return 1 if the system supports at least one terminal type capable of
149 all operations described in
152 .It Li _SC_2_FORT_DEV
153 Return 1 if the system supports the FORTRAN Development Utilities Option,
155 .It Li _SC_2_FORT_RUN
156 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
158 .It Li _SC_2_LOCALEDEF
159 Return 1 if the system supports the creation of locales, otherwise \-1.
161 Return 1 if the system supports the Software Development Utilities Option,
164 Return 1 if the system supports the User Portability Utilities Option,
166 .It Li _SC_AIO_LISTIO_MAX
167 Maximum number of I/O operations in a single list I/O call supported.
169 Maximum number of outstanding asynchronous I/O operations supported.
170 .It Li _SC_AIO_PRIO_DELTA_MAX
171 The maximum amount by which a process can decrease its asynchronous I/O
172 priority level from its own scheduling priority.
173 .It Li _SC_DELAYTIMER_MAX
174 Maximum number of timer expiration overruns.
175 .It Li _SC_MQ_OPEN_MAX
176 The maximum number of open message queue descriptors a process may hold.
178 Maximum number of realtime signals reserved for application use.
179 .It Li _SC_SEM_NSEMS_MAX
180 Maximum number of semaphores that a process may have.
181 .It Li _SC_SEM_VALUE_MAX
182 The maximum value a semaphore may have.
183 .It Li _SC_SIGQUEUE_MAX
184 Maximum number of queued signals that a process may send and have pending at
185 the receiver(s) at any time.
187 Maximum number of timers per process supported.
188 .It Li _SC_GETGR_R_SIZE_MAX
189 Suggested initial value for the size of the group entry buffer.
190 .It Li _SC_GETPW_R_SIZE_MAX
191 Suggested initial value for the size of the password entry buffer.
192 .It Li _SC_HOST_NAME_MAX
193 Maximum length of a host name (not including the terminating null) as
197 .It Li _SC_LOGIN_NAME_MAX
198 Maximum length of a login name.
199 .It Li _SC_THREAD_STACK_MIN
200 Minimum size in bytes of thread stack storage.
201 .It Li _SC_THREAD_THREADS_MAX
202 Maximum number of threads that can be created per process.
203 .It Li _SC_TTY_NAME_MAX
204 Maximum length of terminal device name.
205 .It Li _SC_SYMLOOP_MAX
206 Maximum number of symbolic links that can be reliably traversed in the
207 resolution of a pathname in the absence of a loop.
208 .It Li _SC_ATEXIT_MAX
209 Maximum number of functions that may be registered with
211 .It Li _SC_XOPEN_VERSION
212 An integer value greater than or equal to 4,
213 indicating the version of the X/Open Portability Guide to which this
215 .It Li _SC_XOPEN_XCU_VERSION
216 An integer value indicating the version of the XCU Specification to which
217 this system conforms.
220 These values also exist, but may not be standard:
222 .It Li _SC_CPUSET_SIZE
223 Size of the kernel cpuset.
224 .It Li _SC_PHYS_PAGES
225 The number of pages of physical memory.
226 Note that it is possible that the product of this value and the value of
230 in some configurations on a 32bit machine.
235 is not successful, \-1 is returned and
237 is set appropriately.
238 Otherwise, if the variable is associated with functionality that is not
239 supported, \-1 is returned and
242 Otherwise, the current variable value is returned.
246 function may fail and set
248 for any of the errors specified for the library function
250 In addition, the following error may be reported:
263 Except for the fact that values returned by
265 may change over the lifetime of the calling process,
266 this function conforms to
271 function first appeared in
274 The value for _SC_STREAM_MAX is a minimum maximum, and required to be
275 the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
276 small and misleading number.