man-pages/man3p/fattach.3p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "FATTACH" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" fattach 
.SH NAME
fattach \- attach a STREAMS-based file descriptor to a file in the
file system name space (\fBSTREAMS\fP)
.SH SYNOPSIS
.LP
\fB#include <stropts.h>
.br
.sp
int fattach(int\fP \fIfildes\fP\fB, const char *\fP\fIpath\fP\fB);
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIfattach\fP() function shall attach a STREAMS-based file descriptor
to a file, effectively associating a pathname with
\fIfildes\fP. The application shall ensure that the \fIfildes\fP argument
is a valid open file descriptor associated with a
STREAMS file. The \fIpath\fP argument points to a pathname of an existing
file. The application shall have the appropriate
privileges or be the owner of the file named by \fIpath\fP and have
write permission. A successful call to \fIfattach\fP() shall
cause all pathnames that name the file named by \fIpath\fP to name
the STREAMS file associated with \fIfildes\fP, until the
STREAMS file is detached from the file. A STREAMS file can be attached
to more than one file and can have several pathnames
associated with it.
.LP
The attributes of the named STREAMS file shall be initialized as follows:
the permissions, user ID, group ID, and times are set
to those of the file named by \fIpath\fP, the number of links is set
to 1, and the size and device identifier are set to those of
the STREAMS file associated with \fIfildes\fP. If any attributes of
the named STREAMS file are subsequently changed (for example,
by \fIchmod\fP()), neither the attributes of the underlying file nor
the attributes of the
STREAMS file to which \fIfildes\fP refers shall be affected.
.LP
File descriptors referring to the underlying file, opened prior to
an \fIfattach\fP() call, shall continue to refer to the
underlying file.
.SH RETURN VALUE
.LP
Upon successful completion, \fIfattach\fP() shall return 0. Otherwise,
-1 shall be returned and \fIerrno\fP set to indicate
the error.
.SH ERRORS
.LP
The \fIfattach\fP() function shall fail if:
.TP 7
.B EACCES
Search permission is denied for a component of the path prefix, or
the process is the owner of \fIpath\fP but does not have
write permissions on the file named by \fIpath\fP.
.TP 7
.B EBADF
The \fIfildes\fP argument is not a valid open file descriptor.
.TP 7
.B EBUSY
The file named by \fIpath\fP is currently a mount point or has a STREAMS
file attached to it.
.TP 7
.B ELOOP
A loop exists in symbolic links encountered during resolution of the
\fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
The size of \fIpath\fP exceeds {PATH_MAX} or a component of \fIpath\fP
is longer than {NAME_MAX}.
.TP 7
.B ENOENT
A component of \fIpath\fP does not name an existing file or \fIpath\fP
is an empty string.
.TP 7
.B ENOTDIR
A component of the path prefix is not a directory.
.TP 7
.B EPERM
The effective user ID of the process is not the owner of the file
named by \fIpath\fP and the process does not have
appropriate privilege.
.sp
.LP
The \fIfattach\fP() function may fail if:
.TP 7
.B EINVAL
The \fIfildes\fP argument does not refer to a STREAMS file.
.TP 7
.B ELOOP
More than {SYMLOOP_MAX} symbolic links were encountered during resolution
of the \fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
Pathname resolution of a symbolic link produced an intermediate result
whose length exceeds {PATH_MAX}.
.TP 7
.B EXDEV
A link to a file on another file system was attempted.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Attaching a File Descriptor to a File
.LP
In the following example, \fIfd\fP refers to an open STREAMS file.
The call to \fIfattach\fP() associates this STREAM with the
file \fB/tmp/named-STREAM\fP, such that any future calls to open \fB/tmp/named-STREAM\fP,
prior to breaking the attachment via a
call to \fIfdetach\fP(), will instead create a new file handle referring
to the STREAMS
file associated with \fIfd\fP.
.sp
.RS
.nf

\fB#include <stropts.h>
\&...
    int fd;
    char *filename = "/tmp/named-STREAM";
    int ret;
.sp

    ret = fattach(fd, filename);
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
The \fIfattach\fP() function behaves similarly to the traditional
\fImount\fP() function in the way a file is temporarily
replaced by the root directory of the mounted file system. In the
case of \fIfattach\fP(), the replaced file need not be a
directory and the replacing file is a STREAMS file.
.SH RATIONALE
.LP
The file attributes of a file which has been the subject of an \fIfattach\fP()
call are specifically set because of an artefact
of the original implementation. The internal mechanism was the same
as for the \fImount\fP() function. Since \fImount\fP() is
typically only applied to directories, the effects when applied to
a regular file are a little surprising, especially as regards
the link count which rigidly remains one, even if there were several
links originally and despite the fact that all original links
refer to the STREAM as long as the \fIfattach\fP() remains in effect.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIfdetach\fP() , \fIisastream\fP() , the Base Definitions volume
of
IEEE\ Std\ 1003.1-2001, \fI<stropts.h>\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 .