Originální popis anglicky: getconf - get configuration values

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

getconf [ -v specification ] system_var

getconf [ -v specification ] path_var pathname

POPIS / INSTRUKCE

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 IEEE Std 1003.1-2001 or by the System Interfaces volume of IEEE Std 1003.1-2001 (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 IEEE Std 1003.1-2001, 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_V6_ILP32_OFF32

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


getconf -v POSIX_V6_ILP32_OFF32 ...

determine values for configuration variables corresponding to the POSIX_V6_ILP32_OFF32 compilation environment specified in c99 , the EXTENDED DESCRIPTION.

If the command:


getconf _POSIX_V6_ILP32_OFFBIG

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


getconf -v POSIX_V6_ILP32_OFFBIG ...

determine values for configuration variables corresponding to the POSIX_V6_ILP32_OFFBIG compilation environment specified in c99 , the EXTENDED DESCRIPTION.

If the command:


getconf _POSIX_V6_LP64_OFF64

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


getconf -v POSIX_V6_LP64_OFF64 ...

determine values for configuration variables corresponding to the POSIX_V6_LP64_OFF64 compilation environment specified in c99 , the EXTENDED DESCRIPTION.

If the command:


getconf _POSIX_V6_LPBIG_OFFBIG

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


getconf -v POSIX_V6_LPBIG_OFFBIG ...

determine values for configuration variables corresponding to the POSIX_V6_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 IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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.

PŘÍKLADY POUŽITÍ

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 infinite.
    else
        echo PATH_MAX in /usr is $value.
    fi
else
    echo Error in getconf.
fi

Note that:


sysconf(_SC_POSIX_C_BIND);

and:


system("getconf POSIX2_C_BIND");

in a C program could give different answers. The sysconf() call supplies a value that corresponds to the conditions when the program was either compiled or executed, depending on the implementation; the system() call to getconf always supplies a value corresponding to conditions when the program is executed.

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 IEEE Std 1003.1-2001 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.

SOUVISEJÍCÍ

c99 , the Base Definitions volume of IEEE Std 1003.1-2001, <limits.h>, the System Interfaces volume of IEEE Std 1003.1-2001, confstr(), pathconf(), sysconf(), system()

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .

2003	IEEE/The Open Group