xenial (1) getconf.1posix.gz

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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.1‐2008  or  by  the  System
       Interfaces  volume  of POSIX.1‐2008 (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.1‐2008, 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.1‐2008,  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.1‐2008, 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.1‐2008, 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.1‐2008, 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.1‐2008, 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.1‐2008, 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.1‐2008 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.1‐2008, Chapter 8, Environment Variables, Section 12.2, Utility
       Syntax Guidelines, <limits.h>

       The System Interfaces volume of POSIX.1‐2008, confstr(), fpathconf(), sysconf(), system()

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers,  Inc
       and  The  Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .