man-pages/man1p/getconf.1p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "GETCONF" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" getconf 
.SH NAME
getconf \- get configuration values
.SH SYNOPSIS
.LP
\fBgetconf\fP \fB[\fP \fB-v specification\fP \fB]\fP \fIsystem_var\fP\fB
.br
.sp
getconf\fP \fB[\fP \fB-v specification\fP \fB]\fP \fIpath_var pathname\fP\fB
.br
\fP
.SH DESCRIPTION
.LP
In the first synopsis form, the \fIgetconf\fP utility shall write
to the standard output the value of the variable specified by
the \fIsystem_var\fP operand.
.LP
In the second synopsis form, the \fIgetconf\fP utility shall write
to the standard output the value of the variable specified
by the \fIpath_var\fP operand for the path specified by the \fIpathname\fP
operand.
.LP
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.
.SH OPTIONS
.LP
The \fIgetconf\fP utility shall conform to the Base Definitions volume
of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
.LP
The following option shall be supported:
.TP 7
\fB-v\ \fP \fIspecification\fP
.sp
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. 
.LP
If the command:
.sp
.RS
.nf

\fBgetconf _POSIX_V6_ILP32_OFF32
\fP
.fi
.RE
.LP
does not write \fB"-1\\n"\fP or \fB"undefined\\n"\fP to standard output,
then commands of the form:
.sp
.RS
.nf

\fBgetconf -v POSIX_V6_ILP32_OFF32 ...
\fP
.fi
.RE
.LP
determine values for configuration variables corresponding to the
POSIX_V6_ILP32_OFF32 compilation environment specified in \fIc99\fP
, the EXTENDED DESCRIPTION.
.LP
If the command:
.sp
.RS
.nf

\fBgetconf _POSIX_V6_ILP32_OFFBIG
\fP
.fi
.RE
.LP
does not write \fB"-1\\n"\fP or \fB"undefined\\n"\fP to standard output,
then commands of the form:
.sp
.RS
.nf

\fBgetconf -v POSIX_V6_ILP32_OFFBIG ...
\fP
.fi
.RE
.LP
determine values for configuration variables corresponding to the
POSIX_V6_ILP32_OFFBIG compilation environment specified in \fIc99\fP
, the EXTENDED DESCRIPTION.
.LP
If the command:
.sp
.RS
.nf

\fBgetconf _POSIX_V6_LP64_OFF64
\fP
.fi
.RE
.LP
does not write \fB"-1\\n"\fP or \fB"undefined\\n"\fP to standard output,
then commands of the form:
.sp
.RS
.nf

\fBgetconf -v POSIX_V6_LP64_OFF64 ...
\fP
.fi
.RE
.LP
determine values for configuration variables corresponding to the
POSIX_V6_LP64_OFF64 compilation environment specified in \fIc99\fP
, the EXTENDED DESCRIPTION.
.LP
If the command:
.sp
.RS
.nf

\fBgetconf _POSIX_V6_LPBIG_OFFBIG
\fP
.fi
.RE
.LP
does not write \fB"-1\\n"\fP or \fB"undefined\\n"\fP to standard output,
then commands of the form:
.sp
.RS
.nf

\fBgetconf -v POSIX_V6_LPBIG_OFFBIG ...
\fP
.fi
.RE
.LP
determine values for configuration variables corresponding to the
POSIX_V6_LPBIG_OFFBIG compilation environment specified in \fIc99\fP
, the EXTENDED DESCRIPTION.
.sp
.SH OPERANDS
.LP
The following operands shall be supported:
.TP 7
\fIpath_var\fP
A name of a configuration variable. All of the variables in the Variable
column of the table in the DESCRIPTION of the \fIfpathconf\fP() 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.
.TP 7
\fIpathname\fP
A pathname for which the variable specified by \fIpath_var\fP is to
be determined.
.TP 7
\fIsystem_var\fP
A name of a configuration variable. All of the following variables
shall be supported: 
.RS
.IP " *" 3
The names in the Variable column of the table in the DESCRIPTION of
the \fIsysconf\fP()
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.
.LP
For compatibility with earlier versions, the following variable names
shall also be supported:
.sp
.RS
.nf

POSIX2_C_BIND
POSIX2_C_DEV
POSIX2_CHAR_TERM
POSIX2_FORT_DEV
POSIX2_FORT_RUN
POSIX2_LOCALEDEF
POSIX2_SW_DEV
POSIX2_UPE
POSIX2_VERSION
.fi
.RE
.LP
and shall be equivalent to the same name prefixed with an underscore.
This requirement may be removed in a future version.
.LP
.IP " *" 3
The names of the symbolic constants used as the \fIname\fP argument
of the \fIconfstr\fP() function in the System Interfaces volume of
IEEE\ Std\ 1003.1-2001,
without the _CS_ prefix.
.LP
.IP " *" 3
The names of the symbolic constants listed under the headings ``Maximum
Values'' and ``Minimum Values'' in the description of
the \fI<limits.h>\fP header in the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, without the enclosing braces.
.LP
For compatibility with earlier versions, the following variable names
shall also be supported:
.sp
.RS
.nf

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
.fi
.RE
.LP
and shall be equivalent to the same name prefixed with an underscore.
This requirement may be removed in a future version.
.LP
.RE
.LP
The implementation may add other local values.
.sp
.SH STDIN
.LP
Not used.
.SH INPUT FILES
.LP
None.
.SH ENVIRONMENT VARIABLES
.LP
The following environment variables shall affect the execution of
\fIgetconf\fP:
.TP 7
\fILANG\fP
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.)
.TP 7
\fILC_ALL\fP
If set to a non-empty string value, override the values of all the
other internationalization variables.
.TP 7
\fILC_CTYPE\fP
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).
.TP 7
\fILC_MESSAGES\fP
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
.TP 7
\fINLSPATH\fP
Determine the location of message catalogs for the processing of \fILC_MESSAGES
\&.\fP 
.sp
.SH ASYNCHRONOUS EVENTS
.LP
Default.
.SH STDOUT
.LP
If the specified variable is defined on the system and its value is
described to be available from the \fIconfstr\fP() function defined
in the System Interfaces volume of
IEEE\ Std\ 1003.1-2001, its value shall be written in the following
format:
.sp
.RS
.nf

\fB"%s\\n", <\fP\fIvalue\fP\fB>
\fP
.fi
.RE
.LP
Otherwise, if the specified variable is defined on the system, its
value shall be written in the following format:
.sp
.RS
.nf

\fB"%d\\n", <\fP\fIvalue\fP\fB>
\fP
.fi
.RE
.LP
If the specified variable is valid, but is undefined on the system,
\fIgetconf\fP shall write using the following format:
.sp
.RS
.nf

\fB"undefined\\n"
\fP
.fi
.RE
.LP
If the variable name is invalid or an error occurs, nothing shall
be written to standard output.
.SH STDERR
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
None.
.SH EXTENDED DESCRIPTION
.LP
None.
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
The specified variable is valid and information about its current
state was written successfully.
.TP 7
>0
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
Default.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
None.
.SH EXAMPLES
.LP
The following example illustrates the value of {NGROUPS_MAX}:
.sp
.RS
.nf

\fBgetconf NGROUPS_MAX
\fP
.fi
.RE
.LP
The following example illustrates the value of {NAME_MAX} for a specific
directory:
.sp
.RS
.nf

\fBgetconf NAME_MAX /usr
\fP
.fi
.RE
.LP
The following example shows how to deal more carefully with results
that might be unspecified:
.sp
.RS
.nf

\fBif 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
\fP
.fi
.RE
.LP
Note that:
.sp
.RS
.nf

\fBsysconf(_SC_POSIX_C_BIND);
\fP
.fi
.RE
.LP
and:
.sp
.RS
.nf

\fBsystem("getconf POSIX2_C_BIND");
\fP
.fi
.RE
.LP
in a C program could give different answers. The \fIsysconf\fP() call
supplies a value
that corresponds to the conditions when the program was either compiled
or executed, depending on the implementation; the \fIsystem\fP() call
to \fIgetconf\fP always supplies a value corresponding to conditions
when the
program is executed.
.SH RATIONALE
.LP
The original need for this utility, and for the \fIconfstr\fP() function,
was to
provide a way of finding the configuration-defined default value for
the \fIPATH\fP environment variable. Since \fIPATH\fP 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 \fIPATH\fP 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.
.LP
This functionality of \fIgetconf\fP would not be adequately subsumed
by another command such as:
.sp
.RS
.nf

\fBgrep\fP \fIvar\fP \fB/etc/conf
\fP
.fi
.RE
.LP
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.
.LP
Early proposal versions of \fIgetconf\fP specified exit status 1 when
the specified variable was valid, but not defined on the
system. The output string \fB"undefined"\fP 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.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIc99\fP , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
\fI<limits.h>\fP, the System Interfaces volume of IEEE\ Std\ 1003.1-2001,
\fIconfstr\fP(), \fIpathconf\fP(), \fIsysconf\fP(), \fIsystem\fP()
.SH 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 .