sysconf.3: Document _SC_MQ_{OPEN, PRIO}_MAX.
[dragonfly.git] / lib / libc / gen / sysconf.3
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32.\" @(#)sysconf.3 8.3 (Berkeley) 4/19/94
33.\" $FreeBSD: src/lib/libc/gen/sysconf.3,v 1.8.2.6 2001/12/14 18:33:51 ru Exp $
8a7bdfea 34.\" $DragonFly: src/lib/libc/gen/sysconf.3,v 1.7 2008/05/02 02:05:03 swildner Exp $
984263bc 35.\"
2b9a64c0 36.Dd November 7, 2009
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37.Dt SYSCONF 3
38.Os
39.Sh NAME
40.Nm sysconf
41.Nd get configurable system variables
42.Sh LIBRARY
43.Lb libc
44.Sh SYNOPSIS
45.In unistd.h
46.Ft long
47.Fn sysconf "int name"
48.Sh DESCRIPTION
49This interface is defined by
50.St -p1003.1-88 .
51A far more complete interface is available using
52.Xr sysctl 3 .
53.Pp
54The
55.Fn sysconf
56function provides a method for applications to determine the current
57value of a configurable system limit or option variable.
58The
59.Fa name
60argument specifies the system variable to be queried.
61Symbolic constants for each name value are found in the include file
44cb301e 62.In unistd.h .
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63.Pp
64The available values are as follows:
984263bc 65.Bl -tag -width 6n
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66.It Li _SC_ARG_MAX
67The maximum bytes of argument to
68.Xr execve 2 .
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69.It Li _SC_BC_BASE_MAX
70The maximum ibase/obase values in the
71.Xr bc 1
72utility.
73.It Li _SC_BC_DIM_MAX
74The maximum array size in the
75.Xr bc 1
76utility.
77.It Li _SC_BC_SCALE_MAX
78The maximum scale value in the
79.Xr bc 1
80utility.
81.It Li _SC_BC_STRING_MAX
82The maximum string length in the
83.Xr bc 1
84utility.
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85.It Li _SC_CHILD_MAX
86The maximum number of simultaneous processes per user id.
87.It Li _SC_CLK_TCK
88The frequency of the statistics clock in ticks per second.
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89.It Li _SC_COLL_WEIGHTS_MAX
90The maximum number of weights that can be assigned to any entry of
91the LC_COLLATE order keyword in the locale definition file.
92.It Li _SC_EXPR_NEST_MAX
93The maximum number of expressions that can be nested within
94parenthesis by the
95.Xr expr 1
96utility.
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97.It Li _SC_IOV_MAX
98The maximum number of elements in the I/O vector used by
99.Xr readv 2 ,
100.Xr writev 2 ,
101.Xr recvmsg 2 ,
102and
103.Xr sendmsg 2 .
104.It Li _SC_JOB_CONTROL
105Return 1 if job control is available on this system, otherwise \-1.
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106.It Li _SC_LINE_MAX
107The maximum length in bytes of a text-processing utility's input
108line.
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109.It Li _SC_MQ_OPEN_MAX
110The maximum number of open message queue descriptors per process.
111.It Li _SC_MQ_PRIO_MAX
112The maximum number of message priorities supported by the implementation.
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113.It Li _SC_NGROUPS_MAX
114The maximum number of supplemental groups.
115.It Li _SC_NPROCESSORS_CONF
116The number of processors configured.
117.It Li _SC_NPROCESSORS_ONLN
118The number of processors online.
119.It Li _SC_OPEN_MAX
120The maximum number of open files per user id.
121.It Li _SC_PAGESIZE
122The size of a system page in bytes.
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123.It Li _SC_RE_DUP_MAX
124The maximum number of repeated occurrences of a regular expression
125permitted when using interval notation.
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126.It Li _SC_SAVED_IDS
127Returns 1 if saved set-group and saved set-user ID is available,
128otherwise \-1.
129.It Li _SC_STREAM_MAX
130The minimum maximum number of streams that a process may have open
131at any one time.
132.It Li _SC_TZNAME_MAX
133The minimum maximum number of types supported for the name of a
134timezone.
135.It Li _SC_VERSION
984263bc 136The version of
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137.St -p1003.1
138with which the system
139attempts to comply.
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140.It Li _SC_2_C_BIND
141Return 1 if the system's C-language development facilities support the
142C-Language Bindings Option, otherwise \-1.
143.It Li _SC_2_C_DEV
144Return 1 if the system supports the C-Language Development Utilities Option,
145otherwise \-1.
146.It Li _SC_2_CHAR_TERM
147Return 1 if the system supports at least one terminal type capable of
148all operations described in
149.St -p1003.2 ,
150otherwise \-1.
151.It Li _SC_2_FORT_DEV
152Return 1 if the system supports the FORTRAN Development Utilities Option,
153otherwise \-1.
154.It Li _SC_2_FORT_RUN
155Return 1 if the system supports the FORTRAN Runtime Utilities Option,
156otherwise \-1.
157.It Li _SC_2_LOCALEDEF
158Return 1 if the system supports the creation of locales, otherwise \-1.
159.It Li _SC_2_SW_DEV
160Return 1 if the system supports the Software Development Utilities Option,
161otherwise \-1.
162.It Li _SC_2_UPE
163Return 1 if the system supports the User Portability Utilities Option,
164otherwise \-1.
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165.It Li _SC_2_VERSION
166The version of
167.St -p1003.2
168with which the system attempts to comply.
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169.El
170.Sh RETURN VALUES
171If the call to
172.Fn sysconf
173is not successful, \-1 is returned and
174.Va errno
175is set appropriately.
176Otherwise, if the variable is associated with functionality that is not
177supported, \-1 is returned and
178.Va errno
179is not modified.
180Otherwise, the current variable value is returned.
181.Sh ERRORS
182The
183.Fn sysconf
184function may fail and set
185.Va errno
186for any of the errors specified for the library function
187.Xr sysctl 3 .
188In addition, the following error may be reported:
189.Bl -tag -width Er
190.It Bq Er EINVAL
191The value of the
192.Fa name
193argument is invalid.
194.El
195.Sh SEE ALSO
196.Xr sysctl 3
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197.Sh STANDARDS
198Except for the fact that values returned by
199.Fn sysconf
200may change over the lifetime of the calling process,
201this function conforms to
202.St -p1003.1-88 .
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203.Pp
204_SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are nonstandard, but implemented
205in many systems.
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206.Sh HISTORY
207The
208.Fn sysconf
209function first appeared in
210.Bx 4.4 .
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211.Sh BUGS
212The value for _SC_STREAM_MAX is a minimum maximum, and required to be
213the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
214small and misleading number.