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PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       getconf — get configuration values

SYNOPSIS

       getconf [-v specification] system_var

       getconf [-v specification] path_var pathname

DESCRIPTION

       In  the  first  synopsis  form, the getconf utility shall write to the standard output the
       value of the variable specified by the system_var operand.

       In the second synopsis form, the getconf utility shall write to the  standard  output  the
       value  of  the  variable  specified  by the path_var operand for the path specified by the
       pathname operand.

       The value of each configuration variable shall be determined as if  it  were  obtained  by
       calling  the  function  from  which  it  is  defined  to  be  available  by this volume of
       POSIX.1‐2017 or by  the  System  Interfaces  volume  of  POSIX.1‐2017  (see  the  OPERANDS
       section). The value shall reflect conditions in the current operating environment.

OPTIONS

       The  getconf utility shall conform to the Base Definitions volume of POSIX.1‐2017, Section
       12.2, Utility Syntax Guidelines.

       The following option shall be supported:

       -v specification
                 Indicate a specific specification and version for which configuration  variables
                 shall  be  determined.  If  this  option  is  not specified, the values returned
                 correspond to an implementation default conforming compilation environment.

                 If the command:

                     getconf _POSIX_V7_ILP32_OFF32

                 does not write "-1\n" or "undefined\n" to standard output, then commands of  the
                 form:

                     getconf -v POSIX_V7_ILP32_OFF32 ...

                 determine    values   for   configuration   variables   corresponding   to   the
                 POSIX_V7_ILP32_OFF32 compilation environment  specified  in  c99,  the  EXTENDED
                 DESCRIPTION.

                 If the command:

                     getconf _POSIX_V7_ILP32_OFFBIG

                 does  not write "-1\n" or "undefined\n" to standard output, then commands of the
                 form:

                     getconf -v POSIX_V7_ILP32_OFFBIG ...

                 determine   values   for   configuration   variables   corresponding   to    the
                 POSIX_V7_ILP32_OFFBIG  compilation  environment  specified  in c99, the EXTENDED
                 DESCRIPTION.

                 If the command:

                     getconf _POSIX_V7_LP64_OFF64

                 does not write "-1\n" or "undefined\n" to standard output, then commands of  the
                 form:

                     getconf -v POSIX_V7_LP64_OFF64 ...

                 determine    values   for   configuration   variables   corresponding   to   the
                 POSIX_V7_LP64_OFF64 compilation  environment  specified  in  c99,  the  EXTENDED
                 DESCRIPTION.

                 If the command:

                     getconf _POSIX_V7_LPBIG_OFFBIG

                 does  not write "-1\n" or "undefined\n" to standard output, then commands of the
                 form:

                     getconf -v POSIX_V7_LPBIG_OFFBIG ...

                 determine   values   for   configuration   variables   corresponding   to    the
                 POSIX_V7_LPBIG_OFFBIG  compilation  environment  specified  in c99, the EXTENDED
                 DESCRIPTION.

OPERANDS

       The following operands shall be supported:

       path_var  A name of a configuration variable. All of the variables in the Variable  column
                 of  the  table  in  the  DESCRIPTION  of the fpathconf() function defined in the
                 System Interfaces volume of POSIX.1‐2017, without the enclosing braces, shall be
                 supported. The implementation may add other local variables.

       pathname  A pathname for which the variable specified by path_var is to be determined.

       system_var
                 A  name  of  a  configuration  variable. All of the following variables shall be
                 supported:

                  *  The names in the Variable column of the table  in  the  DESCRIPTION  of  the
                     sysconf()  function  in the System Interfaces volume of POSIX.1‐2017, except
                     for the entries  corresponding  to  _SC_CLK_TCK,  _SC_GETGR_R_SIZE_MAX,  and
                     _SC_GETPW_R_SIZE_MAX, without the enclosing braces.

                     For  compatibility with earlier versions, the following variable names shall
                     also   be    supported:    POSIX2_C_BIND    POSIX2_C_DEV    POSIX2_CHAR_TERM
                     POSIX2_FORT_DEV  POSIX2_FORT_RUN  POSIX2_LOCALEDEF  POSIX2_SW_DEV POSIX2_UPE
                     POSIX2_VERSION

                     and shall be equivalent to the same  name  prefixed  with  an  <underscore>.
                     This requirement may be removed in a future version.

                  *  The  names  of  the  symbolic  constants  used  as  the name argument of the
                     confstr() function in the System Interfaces volume of POSIX.1‐2017,  without
                     the _CS_ prefix.

                  *  The  names  of  the  symbolic  constants listed under the headings ``Maximum
                     Values'' and ``Minimum Values'' in the description of the <limits.h>  header
                     in  the  Base  Definitions  volume  of  POSIX.1‐2017,  without the enclosing
                     braces.

                     For compatibility with earlier versions, the following variable names  shall
                     also  be supported: POSIX2_BC_BASE_MAX POSIX2_BC_DIM_MAX POSIX2_BC_SCALE_MAX
                     POSIX2_BC_STRING_MAX      POSIX2_COLL_WEIGHTS_MAX       POSIX2_EXPR_NEST_MAX
                     POSIX2_LINE_MAX POSIX2_RE_DUP_MAX

                     and  shall  be  equivalent  to  the same name prefixed with an <underscore>.
                     This requirement may be removed in a future version.

                 The implementation may add other local values.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of getconf:

       LANG      Provide a default value for the internationalization variables that are unset or
                 null.   (See   the   Base  Definitions  volume  of  POSIX.1‐2017,  Section  8.2,
                 Internationalization  Variables  for  the  precedence  of   internationalization
                 variables used to determine the values of locale categories.)

       LC_ALL    If  set  to  a  non-empty  string  value,  override  the values of all the other
                 internationalization variables.

       LC_CTYPE  Determine the locale for the interpretation of sequences of bytes of  text  data
                 as  characters  (for example, single-byte as opposed to multi-byte characters in
                 arguments).

       LC_MESSAGES
                 Determine the locale that should be used to affect the format  and  contents  of
                 diagnostic messages written to standard error.

       NLSPATH   Determine the location of message catalogs for the processing of LC_MESSAGES.

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       If  the  specified  variable  is  defined  on  the system and its value is described to be
       available from  the  confstr()  function  defined  in  the  System  Interfaces  volume  of
       POSIX.1‐2017, its value shall be written in the following format:

           "%s\n", <value>

       Otherwise,  if the specified variable is defined on the system, its value shall be written
       in the following format:

           "%d\n", <value>

       If the specified variable is valid, but is undefined on the system,  getconf  shall  write
       using the following format:

           "undefined\n"

       If  the  variable name is invalid or an error occurs, nothing shall be written to standard
       output.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

        0    The specified variable is valid and information about its current state was  written
             successfully.

       >0    An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       None.

EXAMPLES

       The following example illustrates the value of {NGROUPS_MAX}:

           getconf NGROUPS_MAX

       The following example illustrates the value of {NAME_MAX} for a specific directory:

           getconf NAME_MAX /usr

       The  following  example  shows  how  to  deal  more  carefully  with results that might be
       unspecified:

           if value=$(getconf PATH_MAX /usr); then
               if [ "$value" = "undefined" ]; then
                   echo PATH_MAX in /usr is indeterminate.
               else
                   echo PATH_MAX in /usr is $value.
               fi
           else
               echo Error in getconf.
           fi

RATIONALE

       The original need for this utility, and for the confstr() function, was to provide  a  way
       of  finding  the  configuration-defined  default  value for the PATH environment variable.
       Since PATH can be modified by the user to include directories that could contain utilities
       replacing  the  standard  utilities,  shell  scripts  need  a way to determine the system-
       supplied PATH environment variable value that contains the correct  search  path  for  the
       standard utilities. It was later suggested that access to the other variables described in
       this volume of POSIX.1‐2017 could also be useful to applications.

       This functionality of getconf would not be adequately subsumed by another command such as:

           grep var /etc/conf

       because such a strategy would provide correct values for neither those variables that  can
       vary at runtime, nor those that can vary depending on the path.

       Early proposal versions of getconf specified exit status 1 when the specified variable was
       valid, but not defined on the system. The output string "undefined" is now used to specify
       this  case  with exit code 0 because so many things depend on an exit code of zero when an
       invoked utility is successful.

FUTURE DIRECTIONS

       None.

SEE ALSO

       c99

       The Base Definitions volume of POSIX.1‐2017, Chapter  8,  Environment  Variables,  Section
       12.2, Utility Syntax Guidelines, <limits.h>

       The System Interfaces volume of POSIX.1‐2017, confstr(), fpathconf(), sysconf(), system()

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
       the Institute of Electrical and Electronics Engineers, Inc and The  Open  Group.   In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .