mirror of https://github.com/mkerrisk/man-pages
221 lines
6.7 KiB
Plaintext
221 lines
6.7 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
|
|
.TH "CONFSTR" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
|
|
.\" confstr
|
|
.SH NAME
|
|
confstr \- get configurable variables
|
|
.SH SYNOPSIS
|
|
.LP
|
|
\fB#include <unistd.h>
|
|
.br
|
|
.sp
|
|
size_t confstr(int\fP \fIname\fP\fB, char *\fP\fIbuf\fP\fB, size_t\fP
|
|
\fIlen\fP\fB);
|
|
.br
|
|
\fP
|
|
.SH DESCRIPTION
|
|
.LP
|
|
The \fIconfstr\fP() function shall return configuration-defined string
|
|
values. Its use and purpose are similar to \fIsysconf\fP(), but it
|
|
is used where string values rather than numeric values are returned.
|
|
.LP
|
|
The \fIname\fP argument represents the system variable to be queried.
|
|
The implementation shall support the following name
|
|
values, defined in \fI<unistd.h>\fP. It may support others:
|
|
.LP
|
|
.sp
|
|
_CS_PATH
|
|
.br
|
|
_CS_POSIX_V6_ILP32_OFF32_CFLAGS
|
|
.br
|
|
_CS_POSIX_V6_ILP32_OFF32_LDFLAGS
|
|
.br
|
|
_CS_POSIX_V6_ILP32_OFF32_LIBS
|
|
.br
|
|
_CS_POSIX_V6_ILP32_OFFBIG_CFLAGS
|
|
.br
|
|
_CS_POSIX_V6_ILP32_OFFBIG_LDFLAGS
|
|
.br
|
|
_CS_POSIX_V6_ILP32_OFFBIG_LIBS
|
|
.br
|
|
_CS_POSIX_V6_LP64_OFF64_CFLAGS
|
|
.br
|
|
_CS_POSIX_V6_LP64_OFF64_LDFLAGS
|
|
.br
|
|
_CS_POSIX_V6_LP64_OFF64_LIBS
|
|
.br
|
|
_CS_POSIX_V6_LPBIG_OFFBIG_CFLAGS
|
|
.br
|
|
_CS_POSIX_V6_LPBIG_OFFBIG_LDFLAGS
|
|
.br
|
|
_CS_POSIX_V6_LPBIG_OFFBIG_LIBS
|
|
.br
|
|
_CS_POSIX_V6_WIDTH_RESTRICTED_ENVS
|
|
.br
|
|
.sp
|
|
_CS_XBS5_ILP32_OFF32_CFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_ILP32_OFF32_LDFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_ILP32_OFF32_LIBS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_ILP32_OFF32_LINTFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_ILP32_OFFBIG_CFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_ILP32_OFFBIG_LDFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_ILP32_OFFBIG_LIBS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_ILP32_OFFBIG_LINTFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LP64_OFF64_CFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LP64_OFF64_LDFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LP64_OFF64_LIBS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LP64_OFF64_LINTFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LPBIG_OFFBIG_CFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LPBIG_OFFBIG_LDFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LPBIG_OFFBIG_LIBS (\fBLEGACY\fP)
|
|
.br
|
|
_CS_XBS5_LPBIG_OFFBIG_LINTFLAGS (\fBLEGACY\fP)
|
|
.br
|
|
.sp
|
|
.LP
|
|
If \fIlen\fP is not 0, and if \fIname\fP has a configuration-defined
|
|
value, \fIconfstr\fP() shall copy that value into the
|
|
\fIlen\fP-byte buffer pointed to by \fIbuf\fP. If the string to be
|
|
returned is longer than \fIlen\fP bytes, including the
|
|
terminating null, then \fIconfstr\fP() shall truncate the string to
|
|
\fIlen\fP-1 bytes and null-terminate the result. The
|
|
application can detect that the string was truncated by comparing
|
|
the value returned by \fIconfstr\fP() with \fIlen\fP.
|
|
.LP
|
|
If \fIlen\fP is 0 and \fIbuf\fP is a null pointer, then \fIconfstr\fP()
|
|
shall still return the integer value as defined
|
|
below, but shall not return a string. If \fIlen\fP is 0 but \fIbuf\fP
|
|
is not a null pointer, the result is unspecified.
|
|
.LP
|
|
If the implementation supports the POSIX shell option, the string
|
|
stored in \fIbuf\fP after a call to:
|
|
.sp
|
|
.RS
|
|
.nf
|
|
|
|
\fBconfstr(_CS_PATH, buf, sizeof(buf))
|
|
\fP
|
|
.fi
|
|
.RE
|
|
.LP
|
|
can be used as a value of the \fIPATH\fP environment variable that
|
|
accesses all of the standard utilities of
|
|
IEEE\ Std\ 1003.1-2001, if the return value is less than or equal
|
|
to \fIsizeof\fP( \fIbuf\fP).
|
|
.SH RETURN VALUE
|
|
.LP
|
|
If \fIname\fP has a configuration-defined value, \fIconfstr\fP() shall
|
|
return the size of buffer that would be needed to hold
|
|
the entire configuration-defined value including the terminating null.
|
|
If this return value is greater than \fIlen\fP, the string
|
|
returned in \fIbuf\fP is truncated.
|
|
.LP
|
|
If \fIname\fP is invalid, \fIconfstr\fP() shall return 0 and set \fIerrno\fP
|
|
to indicate the error.
|
|
.LP
|
|
If \fIname\fP does not have a configuration-defined value, \fIconfstr\fP()
|
|
shall return 0 and leave \fIerrno\fP
|
|
unchanged.
|
|
.SH ERRORS
|
|
.LP
|
|
The \fIconfstr\fP() function shall fail if:
|
|
.TP 7
|
|
.B EINVAL
|
|
The value of the \fIname\fP argument is invalid.
|
|
.sp
|
|
.LP
|
|
\fIThe following sections are informative.\fP
|
|
.SH EXAMPLES
|
|
.LP
|
|
None.
|
|
.SH APPLICATION USAGE
|
|
.LP
|
|
An application can distinguish between an invalid \fIname\fP parameter
|
|
value and one that corresponds to a configurable
|
|
variable that has no configuration-defined value by checking if \fIerrno\fP
|
|
is modified. This mirrors the behavior of \fIsysconf\fP().
|
|
.LP
|
|
The original need for this function was to provide a way of finding
|
|
the configuration-defined default value for the environment
|
|
variable \fIPATH .\fP Since \fIPATH\fP can be modified by the user
|
|
to include directories that could contain utilities replacing
|
|
the standard utilities in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001,
|
|
applications need a way to determine
|
|
the system-supplied \fIPATH\fP environment variable value that contains
|
|
the correct search path for the standard utilities.
|
|
.LP
|
|
An application could use:
|
|
.sp
|
|
.RS
|
|
.nf
|
|
|
|
\fBconfstr(name, (char *)NULL, (size_t)0)
|
|
\fP
|
|
.fi
|
|
.RE
|
|
.LP
|
|
to find out how big a buffer is needed for the string value; use \fImalloc\fP()
|
|
to
|
|
allocate a buffer to hold the string; and call \fIconfstr\fP() again
|
|
to get the string. Alternately, it could allocate a fixed,
|
|
static buffer that is big enough to hold most answers (perhaps 512
|
|
or 1024 bytes), but then use \fImalloc\fP() to allocate a larger buffer
|
|
if it finds that this is too small.
|
|
.SH RATIONALE
|
|
.LP
|
|
Application developers can normally determine any configuration variable
|
|
by means of reading from the stream opened by a call
|
|
to:
|
|
.sp
|
|
.RS
|
|
.nf
|
|
|
|
\fBpopen("command -p getconf variable", "r");
|
|
\fP
|
|
.fi
|
|
.RE
|
|
.LP
|
|
The \fIconfstr\fP() function with a \fIname\fP argument of _CS_PATH
|
|
returns a string that can be used as a \fIPATH\fP
|
|
environment variable setting that will reference the standard shell
|
|
and utilities as described in the Shell and Utilities volume of
|
|
IEEE\ Std\ 1003.1-2001.
|
|
.LP
|
|
The \fIconfstr\fP() function copies the returned string into a buffer
|
|
supplied by the application instead of returning a
|
|
pointer to a string. This allows a cleaner function in some implementations
|
|
(such as those with lightweight threads) and resolves
|
|
questions about when the application must copy the string returned.
|
|
.SH FUTURE DIRECTIONS
|
|
.LP
|
|
None.
|
|
.SH SEE ALSO
|
|
.LP
|
|
\fIpathconf\fP() , \fIsysconf\fP() , the Base Definitions volume of
|
|
IEEE\ Std\ 1003.1-2001, \fI<unistd.h>\fP, the Shell and Utilities
|
|
volume of
|
|
IEEE\ Std\ 1003.1-2001, \fIc99\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 .
|