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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 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.
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:
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.
The following operands 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.
The following environment variables shall affect the execution of getconf:
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.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
Default.
The following sections are informative.
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.
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.
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()
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