SYSCONF(3)						     Linux Programmer's Manual							SYSCONF(3)

NAME

       sysconf - Get configuration information at runtime

SYNOPSIS

       #include <unistd.h>

       long sysconf(int name);

DESCRIPTION

       sysconf() provides a way for the application to determine values for system limits or options at runtime.

       The  equivalent	macros	defined in <unistd.h> can only give conservative values; if an application wants to take advantage of values which
       may change, a call to sysconf() can be made, which may yield more liberal results.

       For getting information about a particular file, see fpathconf() or pathconf().

       The following values are supported for name.  First, the POSIX.1 compatible values:

       _SC_ARG_MAX
	      The maximum length of the arguments to the exec() family of functions; the corresponding macro is ARG_MAX.

       _SC_CHILD_MAX
	      The number of simultaneous processes per user id, the corresponding macro is CHILD_MAX.

       _SC_CLK_TCK
	      The number of clock ticks per second; the corresponding macro was CLK_TCK.  This	macro  is  obsolete  now.  (Note  that	the  macro
	      CLOCKS_PER_SEC does not give information: it must equal 1000000.)

       _SC_STREAM_MAX
	      The  maximum  number  of	streams that a process can have open at any time.  The corresponding POSIX macro is STREAM_MAX, the corre-
	      sponding standard C macro is FOPEN_MAX.

       _SC_TZNAME_MAX
	      The maximum number of bytes in a timezone name, the corresponding macro is TZNAME_MAX.

       _SC_OPEN_MAX
	      The maximum number of files that a process can have open at any time, the corresponding macro is OPEN_MAX.

       _SC_JOB_CONTROL
	      This indicates whether POSIX - style job control is supported, the corresponding macro is _POSIX_JOB_CONTROL.

       _SC_SAVED_IDS
	      This indicates whether a process has a saved set-user-ID and a saved set-group-ID; the corresponding macro is _POSIX_SAVED_IDS.

       _SC_VERSION
	      indicates the year and month the POSIX.1 standard was approved in the format YYYYMML;the value  199009L  indicates  the  Sept.  1990
	      revision.  The corresponding macro is _POSIX_VERSION.

       Next, the POSIX.2 values:

       _SC_BC_BASE_MAX
	      indicates the maximum obase value accepted by the bc(1) utility; the corresponding macro is BC_BASE_MAX.

       _SC_BC_DIM_MAX
	      indicates the maximum value of elements permitted in an array by bc(1); the corresponding macro is BC_DIM_MAX.

       _SC_BC_SCALE_MAX
	      indicates the maximum scale value allowed by bc(1); the corresponding macro is BC_SCALE_MAX.

       _SC_BC_STRING_MAX
	      indicates the maximum length of a string accepted by bc(1); the corresponding macro is BC_STRING_MAX.

       _SC_COLL_WEIGHTS_MAX
	      indicates  the  maximum numbers of weights that can be assigned to an entry of the LC_COLLATE order keyword in the locale definition
	      file; the corresponding macro is COLL_WEIGHTS_MAX.

       _SC_EXPR_NEST_MAX
	      is the maximum number of expressions which can be nested within parentheses by expr(1).  The corresponding macro is EXPR_NEST_MAX.

       _SC_LINE_MAX
	      The maximum length of a utility's input line length, either from standard input or from a file. This includes length for a  trailing
	      newline.	The corresponding macro is LINE_MAX.

       _SC_RE_DUP_MAX
	      The maximum number of repeated occurrences of a regular expression when the interval notation {m,n} is used. The value of the cor-
	      responding macro is RE_DUP_MAX.

       _SC_2_VERSION
	      indicates the version of the POSIX.2 standard in the format of YYYYMML.  The corresponding macro is POSIX2_VERSION.

       _SC_2_DEV
	      indicates whether the POSIX.2 C language development facilities are supported.  The corresponding macro is POSIX2_C_DEV.

       _SC_2_FORT_DEV
	      indicates whether the POSIX.2 FORTRAN development utilities are supported.  The corresponding macro is POSIX2_FORT_RUN.

       _SC_2_FORT_RUN
	      indicates whether the POSIX.2 FORTRAN runtime utilities are supported.  The corresponding macro is POSIX2_FORT_RUN.

       _SC_2_LOCALEDEF
	      indicates whether the POSIX.2 creation of locates via localedef(1) is supported.	The corresponding macro is _POSIX2_LOCALEDEF.

       _SC_2_SW_DEV
	      indicates whether the POSIX.2 software development utilities option is supported.  The corresponding macro is POSIX2_SW_DEV.

       SUSv2 also lists

       _SC_PAGESIZE _SC_PAGE_SIZE
	      The size of a page (in bytes).

       These values also exist, but may not be standard.

       _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  _SC_PAGE_SIZE	to
	      overflow.

       _SC_AVPHYS_PAGES
	      The number of currently available pages of physical memory.

RETURN VALUE

       If  name is invalid, -1 is returned, and errno is set to EINVAL.  Otherwise, the value returned is the value of the system resource, 1 if a
       queried option is available, 0 if it is not, or -1 on error, and the variable errno is not changed.

CONFORMING TO

       POSIX.1.

BUGS

       It is difficult to use ARG_MAX because it is not specified how much of the argument space for exec() is consumed by the user's  environment
       variables.

       Some returned values may be huge; they are not suitable for allocating memory.

SEE ALSO

       bc(1), expr(1), locale(1), fpathconf(3), pathconf(3)

GNU
								    1993-04-18								SYSCONF(3)