getconf(1posix)
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.12008 or by the System Interfaces volume of POSIX.12008 (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.12008, 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.12008, 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.12008, 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.12008, 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.12008, 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.12008, 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.12008, 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.12008
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.12008, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines, <limits.h> The System Interfaces volume of POSIX.12008, confstr(), fpathconf(), sysconf(), system()
COPYRIGHT
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 .
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