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    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 _POSIX_CHILD_MAX.

           _SC_CLK_TCK
                  The number of clock ticks per  second;  the  corre-
                  sponding macro is CLK_TCK.

           _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 corresponding 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
                  _POSIX_OPEN_MAX.

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

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                  _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 most recent revision, 1990.

           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  corre-
                  sponding 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  corre-
                  sponding 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  corresponding
                  macro is RE_DUP_MAX.

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           _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 develop-
                  ment 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 util-
                  ities are supported.  The  corresponding  macro  is
                  POSIX2_FORT_RUN.

           POSIX2_LOCALEDEF
                  indicates  whether  the POSIX.2 creation of locates
                  via  locale(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.

    RETURN VALUE
           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.  The variable errno is not set.

    CONFORMS TO
           POSIX.1, proposed POSIX.2

    BUGS
           It  is  difficult  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.

           POSIX.2 is not yet an approved standard;  the  information
           in this manpage is subject to change.

### SEE ALSO

bc, expr, locale, fpathconf, pathconf,

###

    GNU                       April 18, 1993                        3

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