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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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GETCONF(1P) POSIX Programmer's Manual GETCONF(1P)
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.
getconf — get configuration values
getconf [-v specification] system_var
getconf [-v specification] path_var pathname
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.
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.
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.
Not used.
None.
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.
Default.
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.
The standard error shall be used only for diagnostic messages.
None.
None.
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.
Default.
The following sections are informative.
None.
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
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.
None.
c99(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines,
limits.h(0p)
The System Interfaces volume of POSIX.1‐2017, confstr(3p),
fpathconf(3p), sysconf(3p), system(3p)
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 .
IEEE/The Open Group 2017 GETCONF(1P)
Pages that refer to this page: poll.h(0p), stddef.h(0p), sys_types.h(0p), termios.h(0p), wchar.h(0p), c99(1p), fincore(1), fpathconf(3p), sysconf(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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