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[dragonfly.git] / lib / libc / gen / sysconf.3
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1.\" Copyright (c) 1993
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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 $
44cb301e 34.\" $DragonFly: src/lib/libc/gen/sysconf.3,v 1.5 2006/05/26 19:39:36 swildner Exp $
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35.\"
36.Dd April 19, 1994
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:
65.Pp
66.Bl -tag -width 6n
67.Pp
68.It Li _SC_ARG_MAX
69The maximum bytes of argument to
70.Xr execve 2 .
71.It Li _SC_CHILD_MAX
72The maximum number of simultaneous processes per user id.
73.It Li _SC_CLK_TCK
74The frequency of the statistics clock in ticks per second.
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75.It Li _SC_IOV_MAX
76The maximum number of elements in the I/O vector used by
77.Xr readv 2 ,
78.Xr writev 2 ,
79.Xr recvmsg 2 ,
80and
81.Xr sendmsg 2 .
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82.It Li _SC_NGROUPS_MAX
83The maximum number of supplemental groups.
84.It Li _SC_OPEN_MAX
85The maximum number of open files per user id.
86.It Li _SC_STREAM_MAX
87The minimum maximum number of streams that a process may have open
88at any one time.
89.It Li _SC_TZNAME_MAX
90The minimum maximum number of types supported for the name of a
91timezone.
92.It Li _SC_JOB_CONTROL
93Return 1 if job control is available on this system, otherwise \-1.
94.It Li _SC_SAVED_IDS
95Returns 1 if saved set-group and saved set-user ID is available,
96otherwise \-1.
97.It Li _SC_VERSION
98The version of
99.St -p1003.1
100with which the system
101attempts to comply.
102.It Li _SC_BC_BASE_MAX
103The maximum ibase/obase values in the
104.Xr bc 1
105utility.
106.It Li _SC_BC_DIM_MAX
107The maximum array size in the
108.Xr bc 1
109utility.
110.It Li _SC_BC_SCALE_MAX
111The maximum scale value in the
112.Xr bc 1
113utility.
114.It Li _SC_BC_STRING_MAX
115The maximum string length in the
116.Xr bc 1
117utility.
118.It Li _SC_COLL_WEIGHTS_MAX
119The maximum number of weights that can be assigned to any entry of
120the LC_COLLATE order keyword in the locale definition file.
121.It Li _SC_EXPR_NEST_MAX
122The maximum number of expressions that can be nested within
123parenthesis by the
124.Xr expr 1
125utility.
126.It Li _SC_LINE_MAX
127The maximum length in bytes of a text-processing utility's input
128line.
129.It Li _SC_RE_DUP_MAX
130The maximum number of repeated occurrences of a regular expression
131permitted when using interval notation.
132.It Li _SC_2_VERSION
133The version of
134.St -p1003.2
135with which the system attempts to comply.
136.It Li _SC_2_C_BIND
137Return 1 if the system's C-language development facilities support the
138C-Language Bindings Option, otherwise \-1.
139.It Li _SC_2_C_DEV
140Return 1 if the system supports the C-Language Development Utilities Option,
141otherwise \-1.
142.It Li _SC_2_CHAR_TERM
143Return 1 if the system supports at least one terminal type capable of
144all operations described in
145.St -p1003.2 ,
146otherwise \-1.
147.It Li _SC_2_FORT_DEV
148Return 1 if the system supports the FORTRAN Development Utilities Option,
149otherwise \-1.
150.It Li _SC_2_FORT_RUN
151Return 1 if the system supports the FORTRAN Runtime Utilities Option,
152otherwise \-1.
153.It Li _SC_2_LOCALEDEF
154Return 1 if the system supports the creation of locales, otherwise \-1.
155.It Li _SC_2_SW_DEV
156Return 1 if the system supports the Software Development Utilities Option,
157otherwise \-1.
158.It Li _SC_2_UPE
159Return 1 if the system supports the User Portability Utilities Option,
160otherwise \-1.
161.El
162.Sh RETURN VALUES
163If the call to
164.Fn sysconf
165is not successful, \-1 is returned and
166.Va errno
167is set appropriately.
168Otherwise, if the variable is associated with functionality that is not
169supported, \-1 is returned and
170.Va errno
171is not modified.
172Otherwise, the current variable value is returned.
173.Sh ERRORS
174The
175.Fn sysconf
176function may fail and set
177.Va errno
178for any of the errors specified for the library function
179.Xr sysctl 3 .
180In addition, the following error may be reported:
181.Bl -tag -width Er
182.It Bq Er EINVAL
183The value of the
184.Fa name
185argument is invalid.
186.El
187.Sh SEE ALSO
188.Xr sysctl 3
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189.Sh STANDARDS
190Except for the fact that values returned by
191.Fn sysconf
192may change over the lifetime of the calling process,
193this function conforms to
194.St -p1003.1-88 .
195.Sh HISTORY
196The
197.Fn sysconf
198function first appeared in
199.Bx 4.4 .
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200.Sh BUGS
201The value for _SC_STREAM_MAX is a minimum maximum, and required to be
202the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously
203small and misleading number.