+++ /dev/null
-.\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.\" Modified Sat Jul 24 17:51:42 1993 by Rik Faith (faith@cs.unc.edu)
-.\" Modified Tue Aug 17 11:42:20 1999 by Ariel Scolnicov (ariels@compugen.co.il)
-.TH SYSCONF 3 2014-12-31 "GNU" "Linux Programmer's Manual"
-.SH NAME
-sysconf \- get configuration information at run time
-.SH SYNOPSIS
-.nf
-.B #include <unistd.h>
-.sp
-.BI "long sysconf(int " "name" );
-.fi
-.SH DESCRIPTION
-POSIX allows an application to test at compile or run time
-whether certain options are supported, or what the value is
-of certain configurable constants or limits.
-.LP
-At compile time this is done by including
-.I <unistd.h>
-and/or
-.I <limits.h>
-and testing the value of certain macros.
-.LP
-At run time, one can ask for numerical values using the present function
-.BR sysconf ().
-One can ask for numerical values that may depend
-on the filesystem a file is in using the calls
-.BR fpathconf (3)
-and
-.BR pathconf (3).
-One can ask for string values using
-.BR confstr (3).
-.LP
-The values obtained from these functions are system configuration constants.
-They do not change during the lifetime of a process.
-.\" except that sysconf(_SC_OPEN_MAX) may change answer after a call
-.\" to setrlimit( ) which changes the RLIMIT_NOFILE soft limit
-.LP
-For options, typically, there is a constant
-.B _POSIX_FOO
-that may be defined in
-.IR <unistd.h> .
-If it is undefined, one should ask at run time.
-If it is defined to \-1, then the option is not supported.
-If it is defined to 0, then relevant functions and headers exist,
-but one has to ask at run time what degree of support is available.
-If it is defined to a value other than \-1 or 0, then the option is
-supported.
-Usually the value (such as 200112L) indicates the year and month
-of the POSIX revision describing the option.
-Glibc uses the value 1
-to indicate support as long as the POSIX revision has not been published yet.
-.\" and 999 to indicate support for options no longer present in the latest
-.\" standard. (?)
-The
-.BR sysconf ()
-argument will be
-.BR _SC_FOO .
-For a list of options, see
-.BR posixoptions (7).
-.LP
-For variables or limits, typically, there is a constant
-.BR _FOO ,
-maybe defined in
-.IR <limits.h> ,
-or
-.BR _POSIX_FOO ,
-maybe defined in
-.IR <unistd.h> .
-The constant will not be defined if the limit is unspecified.
-If the constant is defined, it gives a guaranteed value, and
-a greater value might actually be supported.
-If an application wants to take advantage of values which may change
-between systems, a call to
-.BR sysconf ()
-can be made.
-The
-.BR sysconf ()
-argument will be
-.BR _SC_FOO .
-.SS POSIX.1 variables
-We give the name of the variable, the name of the
-.BR sysconf ()
-argument used to inquire about its value,
-and a short description.
-.LP
-First, the POSIX.1 compatible values.
-.\" [for the moment: only the things that are unconditionally present]
-.\" .TP
-.\" .BR AIO_LISTIO_MAX " - " _SC_AIO_LISTIO_MAX
-.\" (if _POSIX_ASYNCHRONOUS_IO)
-.\" Maximum number of I/O operations in a single list I/O call.
-.\" Must not be less than _POSIX_AIO_LISTIO_MAX.
-.\" .TP
-.\" .BR AIO_MAX " - " _SC_AIO_MAX
-.\" (if _POSIX_ASYNCHRONOUS_IO)
-.\" Maximum number of outstanding asynchronous I/O operations.
-.\" Must not be less than _POSIX_AIO_MAX.
-.\" .TP
-.\" .BR AIO_PRIO_DELTA_MAX " - " _SC_AIO_PRIO_DELTA_MAX
-.\" (if _POSIX_ASYNCHRONOUS_IO)
-.\" The maximum amount by which a process can decrease its
-.\" asynchronous I/O priority level from its own scheduling priority.
-.\" Must be nonnegative.
-.TP
-.BR ARG_MAX " - " _SC_ARG_MAX
-The maximum length of the arguments to the
-.BR exec (3)
-family of functions.
-Must not be less than
-.B _POSIX_ARG_MAX
-(4096).
-.TP
-.BR CHILD_MAX " - " _SC_CHILD_MAX
-The maximum number of simultaneous processes per user ID.
-Must not be less than
-.B _POSIX_CHILD_MAX
-(25).
-.TP
-.BR HOST_NAME_MAX " - " _SC_HOST_NAME_MAX
-Maximum length of a hostname, not including the terminating null byte,
-as returned by
-.BR gethostname (2).
-Must not be less than
-.B _POSIX_HOST_NAME_MAX
-(255).
-.TP
-.BR LOGIN_NAME_MAX " - " _SC_LOGIN_NAME_MAX
-Maximum length of a login name, including the terminating null byte.
-Must not be less than
-.B _POSIX_LOGIN_NAME_MAX
-(9).
-.TP
-.BR NGROUPS_MAX " - " _SC_NGROUPS_MAX
-Maximum number of supplementary group IDs.
-.TP
-.BR "" "clock ticks - " _SC_CLK_TCK
-The number of clock ticks per second.
-The corresponding variable is obsolete.
-It was of course called
-.BR CLK_TCK .
-(Note: the macro
-.B CLOCKS_PER_SEC
-does not give information: it must equal 1000000.)
-.TP
-.BR OPEN_MAX " - " _SC_OPEN_MAX
-The maximum number of files that a process can have open at any time.
-Must not be less than
-.B _POSIX_OPEN_MAX
-(20).
-.TP
-.BR PAGESIZE " - " _SC_PAGESIZE
-Size of a page in bytes.
-Must not be less than 1.
-(Some systems use PAGE_SIZE instead.)
-.TP
-.BR RE_DUP_MAX " - " _SC_RE_DUP_MAX
-The number of repeated occurrences of a BRE permitted by
-.BR regexec (3)
-and
-.BR regcomp (3).
-Must not be less than
-.B _POSIX2_RE_DUP_MAX
-(255).
-.TP
-.BR STREAM_MAX " - " _SC_STREAM_MAX
-The maximum number of streams that a process can have open at any
-time.
-If defined, it has the same value as the standard C macro
-.BR FOPEN_MAX .
-Must not be less than
-.B _POSIX_STREAM_MAX
-(8).
-.TP
-.BR SYMLOOP_MAX " - " _SC_SYMLOOP_MAX
-The maximum number of symbolic links seen in a pathname before resolution
-returns
-.BR ELOOP .
-Must not be less than
-.B _POSIX_SYMLOOP_MAX
-(8).
-.TP
-.BR TTY_NAME_MAX " - " _SC_TTY_NAME_MAX
-The maximum length of terminal device name,
-including the terminating null byte.
-Must not be less than
-.B _POSIX_TTY_NAME_MAX
-(9).
-.TP
-.BR TZNAME_MAX " - " _SC_TZNAME_MAX
-The maximum number of bytes in a timezone name.
-Must not be less than
-.B _POSIX_TZNAME_MAX
-(6).
-.TP
-.BR _POSIX_VERSION " - " _SC_VERSION
-indicates the year and month the POSIX.1 standard was approved in the
-format
-.BR YYYYMML ;
-the value
-.B 199009L
-indicates the Sept. 1990 revision.
-.SS POSIX.2 variables
-Next, the POSIX.2 values, giving limits for utilities.
-.TP
-.BR BC_BASE_MAX " - " _SC_BC_BASE_MAX
-indicates the maximum
-.I obase
-value accepted by the
-.BR bc (1)
-utility.
-.TP
-.BR BC_DIM_MAX " - " _SC_BC_DIM_MAX
-indicates the maximum value of elements permitted in an array by
-.BR bc (1).
-.TP
-.BR BC_SCALE_MAX " - " _SC_BC_SCALE_MAX
-indicates the maximum
-.I scale
-value allowed by
-.BR bc (1).
-.TP
-.BR BC_STRING_MAX " - " _SC_BC_STRING_MAX
-indicates the maximum length of a string accepted by
-.BR bc (1).
-.TP
-.BR COLL_WEIGHTS_MAX " - " _SC_COLL_WEIGHTS_MAX
-indicates the maximum numbers of weights that can be assigned to an
-entry of the
-.B LC_COLLATE order
-keyword in the locale definition file,
-.TP
-.BR EXPR_NEST_MAX " - " _SC_EXPR_NEST_MAX
-is the maximum number of expressions which can be nested within
-parentheses by
-.BR expr (1).
-.TP
-.BR LINE_MAX " - " _SC_LINE_MAX
-The maximum length of a utility's input line, either from
-standard input or from a file.
-This includes space for a trailing
-newline.
-.TP
-.BR RE_DUP_MAX " - " _SC_RE_DUP_MAX
-The maximum number of repeated occurrences of a regular expression when
-the interval notation
-.B \e{m,n\e}
-is used.
-.TP
-.BR POSIX2_VERSION " - " _SC_2_VERSION
-indicates the version of the POSIX.2 standard in the format of
-YYYYMML.
-.TP
-.BR POSIX2_C_DEV " - " _SC_2_C_DEV
-indicates whether the POSIX.2 C language development facilities are
-supported.
-.TP
-.BR POSIX2_FORT_DEV " - " _SC_2_FORT_DEV
-indicates whether the POSIX.2 FORTRAN development utilities are
-supported.
-.TP
-.BR POSIX2_FORT_RUN " - " _SC_2_FORT_RUN
-indicates whether the POSIX.2 FORTRAN run-time utilities are supported.
-.TP
-.BR _POSIX2_LOCALEDEF " - " _SC_2_LOCALEDEF
-indicates whether the POSIX.2 creation of locates via
-.BR localedef (1)
-is supported.
-.TP
-.BR POSIX2_SW_DEV " - " _SC_2_SW_DEV
-indicates whether the POSIX.2 software development utilities option is
-supported.
-.PP
-These values also exist, but may not be standard.
-.TP
-.BR "" " - " _SC_PHYS_PAGES
-The number of pages of physical memory.
-Note that it is possible
-for the product of this value and the value of
-.B _SC_PAGESIZE
-to overflow.
-.TP
-.BR "" " - " _SC_AVPHYS_PAGES
-The number of currently available pages of physical memory.
-.TP
-.BR "" " - " _SC_NPROCESSORS_CONF
-The number of processors configured.
-.TP
-.BR "" " - " _SC_NPROCESSORS_ONLN
-The number of processors currently online (available).
-.SH RETURN VALUE
-If
-.I name
-is invalid, \-1 is returned, and
-.I errno
-is set to
-.BR EINVAL .
-Otherwise, the value returned is the value of the system resource and
-.I errno
-is not changed.
-In the case of options, a positive value is returned if a queried option
-is available, and \-1 if it is not.
-In the case of limits, \-1 means that there is no definite limit.
-.SH CONFORMING TO
-POSIX.1-2001.
-.SH BUGS
-It is difficult to use
-.B ARG_MAX
-because it is not specified how much of the argument space for
-.BR exec (3)
-is consumed by the user's environment variables.
-.PP
-Some returned values may be huge; they are not suitable for allocating
-memory.
-.SH SEE ALSO
-.BR bc (1),
-.BR expr (1),
-.BR getconf (1),
-.BR locale (1),
-.BR confstr (3),
-.BR fpathconf (3),
-.BR pathconf (3),
-.BR posixoptions (7)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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