# getconf

## 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(1p), 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(1p), 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(1p), 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(1p), 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.
    


* * *