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.TH FATTACH "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

This manual page is part of the POSIX Programmer's Manual.

The Linux implementation of this interface may differ (consult

the corresponding Linux manual page for details of Linux behavior),

or the interface may not be implemented on Linux.

.SH NAME

fattach

\(em attach a STREAMS-based file descriptor to a file in the

file system name space (\fBSTREAMS\fP)

.SH SYNOPSIS

.LP

.nf

#include <stropts.h>

.P

int fattach(int \fIfildes\fP, const char *\fIpath\fP);

.fi

.SH DESCRIPTION

The

\fIfattach\fR()

function shall attach a STREAMS-based file descriptor to a file,

effectively associating a pathname with

.IR fildes .

The application shall ensure that the

.IR fildes

argument is a valid open file descriptor associated with a STREAMS

file. The

.IR path

argument points to a pathname of an existing file. The application

shall have appropriate privileges or be the owner of the file

named by

.IR path

and have write permission. A successful call to

\fIfattach\fR()

shall cause all pathnames that name the file named by

.IR path

to name the STREAMS file associated with

.IR fildes ,

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.

.P

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

.IR path ,

the number of links is set to 1, and the size and device identifier are

set to those of the STREAMS file associated with

.IR fildes .

If any attributes of the named STREAMS file are subsequently changed

(for example, by

\fIchmod\fR()),

neither the attributes of the underlying file nor the attributes of the

STREAMS file to which

.IR fildes

refers shall be affected.

.P

File descriptors referring to the underlying file, opened prior to an

\fIfattach\fR()

call, shall continue to refer to the underlying file.

.SH "RETURN VALUE"

Upon successful completion,

\fIfattach\fR()

shall return 0. Otherwise, \(mi1 shall be returned and

.IR errno

set to indicate the error.

.SH ERRORS

The

\fIfattach\fR()

function shall fail if:

.TP

.BR EACCES

Search permission is denied for a component of the path prefix, or the

process is the owner of

.IR path

but does not have write permissions on the file named by

.IR path .

.TP

.BR EBADF

The

.IR fildes

argument is not a valid open file descriptor.

.TP

.BR EBUSY

The file named by

.IR path

is currently a mount point or has a STREAMS file attached to it.

.TP

.BR ELOOP

A loop exists in symbolic links encountered during resolution of the

.IR path

argument.

.TP

.BR ENAMETOOLONG

.br

The length of a component of a pathname is longer than

{NAME_MAX}.

.TP

.BR ENOENT

A component of

.IR path

does not name an existing file or

.IR path

is an empty string.

.TP

.BR ENOTDIR

A component of the path prefix names an existing file that is neither

a directory nor a symbolic link to a directory, or the

.IR path

argument contains at least one non-\c

<slash>

character and ends with one or more trailing

<slash>

characters.

.TP

.BR EPERM

The effective user ID of the process is not the owner of the file named

by

.IR path

and the process does not have appropriate privileges.

.br

.P

The

\fIfattach\fR()

function may fail if:

.TP

.BR EINVAL

The

.IR fildes

argument does not refer to a STREAMS file.

.TP

.BR ELOOP

More than

{SYMLOOP_MAX}

symbolic links were encountered during resolution of the

.IR path

argument.

.TP

.BR ENAMETOOLONG

.br

The length of a pathname exceeds

{PATH_MAX},

or pathname resolution of a symbolic link produced an intermediate

result with a length that exceeds

{PATH_MAX}.

.TP

.BR EXDEV

A link to a file on another file system was attempted.

.LP

.IR "The following sections are informative."

.SH EXAMPLES

.SS "Attaching a File Descriptor to a File"

.P

In the following example,

.IR fd

refers to an open STREAMS file. The call to

\fIfattach\fR()

associates this STREAM with the file

.BR /tmp/named-STREAM ,

such that any future calls to open

.BR /tmp/named-STREAM ,

prior to breaking the attachment via a call to

\fIfdetach\fR(),

will instead create a new file handle referring to the STREAMS file

associated with

.IR fd .

.sp

.RS 4

.nf

\fB

#include <stropts.h>

\&...

    int fd;

    char *pathname = "/tmp/named-STREAM";

    int ret;

.P

    ret = fattach(fd, pathname);

.fi \fR

.P

.RE

.SH "APPLICATION USAGE"

The

\fIfattach\fR()

function behaves similarly to the traditional

\fImount\fR()

function in the way a file is temporarily replaced by the root

directory of the mounted file system. In the case of

\fIfattach\fR(),

the replaced file need not be a directory and the replacing file is a

STREAMS file.

.SH RATIONALE

The file attributes of a file which has been the subject of an

\fIfattach\fR()

call are specifically set because of an artifact of the original

implementation. The internal mechanism was the same as for the

\fImount\fR()

function. Since

\fImount\fR()

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\fR()

remains in effect.

.SH "FUTURE DIRECTIONS"

The

\fIfattach\fR()

function may be removed in a future version.

.SH "SEE ALSO"

.IR "\fIfdetach\fR\^(\|)",

.IR "\fIisastream\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<stropts.h>\fP"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

Any typographical or formatting errors that appear

in this page are most likely

to have been introduced during the conversion of the source files to

man page format. To report such errors, see

https://www.kernel.org/doc/man-pages/reporting_bugs.html .