SYSCONF

Section: C Library Functions (3)
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BSD mandoc
BSD 4

NAME

sysconf - get configurable system variables

SYNOPSIS

Fd #include <unistd.h> Ft long Fn sysconf int name

DESCRIPTION

This interface is defined by St -p1003.1-88 . A far more complete interface is available using sysctl(3).

The Fn sysconf function provides a method for applications to determine the current value of a configurable system limit or option variable. The Fa name argument specifies the system variable to be queried. Symbolic constants for each name value are found in the include file <unistd.h>

The available values are as follows:

_SC_ARG_MAX: The maximum bytes of argument to exec(2).
_SC_CHILD_MAX: The maximum number of simultaneous processes per user id.
_SC_CLK_TCK: Number of micro-seconds per hz tick.
_SC_NGROUPS_MAX: The maximum number of supplemental groups.
_SC_OPEN_MAX: The maximum number of open files per user id.
_SC_STREAM_MAX: The minimum maximum number of streams that a process may have open at any one time.
_SC_TZNAME_MAX: The minimum maximum number of types supported for the name of a timezone.
_SC_JOB_CONTROL: Return 1 if job control is available on this system, otherwise -1.
_SC_SAVED_IDS: Returns 1 if saved set-group and saved set-user ID is available, otherwise -1.
_SC_VERSION: The version of ISO/IEC 9945 (POSIX 1003.1) with which the system attempts to comply.
_SC_BC_BASE_MAX: The maximum ibase/obase values in the bc(1) utility.
_SC_BC_DIM_MAX: The maximum array size in the bc(1) utility.
_SC_BC_SCALE_MAX: The maximum scale value in the bc(1) utility.
_SC_BC_STRING_MAX: The maximum string length in the bc(1) utility.
_SC_COLL_WEIGHTS_MAX: The maximum number of weights that can be assigned to any entry of the LC_COLLATE order keyword in the locale definition file.
_SC_EXPR_NEST_MAX: The maximum number of expressions that can be nested within parenthesis by the expr(1) utility.
_SC_LINE_MAX: The maximum length in bytes of a text-processing utility's input line.
_SC_RE_DUP_MAX: The maximum number of repeated occurrences of a regular expression permitted when using interval notation.
_SC_2_VERSION: The version of POSIX 1003.2 with which the system attempts to comply.
_SC_2_C_BIND: Return 1 if the system's C-language development facilities support the
C-Language Bindings Option, otherwise -1.
_SC_2_C_DEV: Return 1 if the system supports the C-Language Development Utilities Option, otherwise -1.
_SC_2_CHAR_TERM: Return 1 if the system supports at least one terminal type capable of all operations described in POSIX 1003.2, otherwise -1.
_SC_2_FORT_DEV: Return 1 if the system supports the FORTRAN Development Utilities Option, otherwise -1.
_SC_2_FORT_RUN: Return 1 if the system supports the FORTRAN Runtime Utilities Option, otherwise -1.
_SC_2_LOCALEDEF: Return 1 if the system supports the creation of locales, otherwise -1.
_SC_2_SW_DEV: Return 1 if the system supports the Software Development Utilities Option, otherwise -1.
_SC_2_UPE: Return 1 if the system supports the User Portability Utilities Option, otherwise -1.

RETURN VALUES

If the call to sysconf is not successful, -1 is returned and errno is set appropriately. Otherwise, if the variable is associated with functionality that is not supported, -1 is returned and errno is not modified. Otherwise, the current variable value is returned.

ERRORS

The Fn sysconf function may fail and set errno for any of the errors specified for the library functions sysctl(3). In addition, the following error may be reported:

Bq Er EINVAL: The value of the Fa name argument is invalid.

BUGS

The value for _SC_STREAM_MAX is a minimum maximum, and required to be the same as ANSI C's FOPEN_MAX, so the returned value is a ridiculously small and misleading number.

STANDARDS

The Fn sysconf function conforms to St -p1003.1-88 .

HISTORY

The sysconf function first appeared in 4.4BSD.

This document was created by man2html, using the manual pages.
Time: 19:41:58 GMT, December 25, 2022