1FATTACH(3P) POSIX Programmer's Manual FATTACH(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 fattach — attach a STREAMS-based file descriptor to a file in the file
13 system name space (STREAMS)
14
16 #include <stropts.h>
17 int fattach(int fildes, const char *path);
19
21 The fattach() function shall attach a STREAMS-based file descriptor to
22 a file, effectively associating a pathname with fildes. The applica‐
23 tion shall ensure that the fildes argument is a valid open file
24 descriptor associated with a STREAMS file. The path argument points to
25 a pathname of an existing file. The application shall have appropriate
26 privileges or be the owner of the file named by path and have write
27 permission. A successful call to fattach() shall cause all pathnames
28 that name the file named by path to name the STREAMS file associated
29 with fildes, until the STREAMS file is detached from the file. A
30 STREAMS file can be attached to more than one file and can have several
31 pathnames associated with it.
32 The attributes of the named STREAMS file shall be initialized as fol‐
34 lows: the permissions, user ID, group ID, and times are set to those of
35 the file named by path, the number of links is set to 1, and the size
36 and device identifier are set to those of the STREAMS file associated
37 with fildes. If any attributes of the named STREAMS file are subse‐
38 quently changed (for example, by chmod()), neither the attributes of
39 the underlying file nor the attributes of the STREAMS file to which
40 fildes refers shall be affected.
41 File descriptors referring to the underlying file, opened prior to an
43 fattach() call, shall continue to refer to the underlying file.
44
46 Upon successful completion, fattach() shall return 0. Otherwise, -1
47 shall be returned and errno set to indicate the error.
48
50 The fattach() function shall fail if:
51 EACCES Search permission is denied for a component of the path prefix,
53 or the process is the owner of path but does not have write per‐
54 missions on the file named by path.
55 EBADF The fildes argument is not a valid open file descriptor.
57 EBUSY The file named by path is currently a mount point or has a
59 STREAMS file attached to it.
60 ELOOP A loop exists in symbolic links encountered during resolution of
62 the path argument.
63 ENAMETOOLONG
65 The length of a component of a pathname is longer than
66 {NAME_MAX}.
67 ENOENT A component of path does not name an existing file or path is an
69 empty string.
70 ENOTDIR
72 A component of the path prefix names an existing file that is
73 neither a directory nor a symbolic link to a directory, or the
74 path argument contains at least one non-<slash> character and
75 ends with one or more trailing <slash> characters.
76 EPERM The effective user ID of the process is not the owner of the
78 file named by path and the process does not have appropriate
79 privileges.
80 The fattach() function may fail if:
82 EINVAL The fildes argument does not refer to a STREAMS file.
84 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
86 resolution of the path argument.
87 ENAMETOOLONG
89 The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
90 tion of a symbolic link produced an intermediate result with a
91 length that exceeds {PATH_MAX}.
92 EXDEV A link to a file on another file system was attempted.
94 The following sections are informative.
96
98 Attaching a File Descriptor to a File
99 In the following example, fd refers to an open STREAMS file. The call
100 to fattach() associates this STREAM with the file /tmp/named-STREAM,
101 such that any future calls to open /tmp/named-STREAM, prior to breaking
102 the attachment via a call to fdetach(), will instead create a new file
103 handle referring to the STREAMS file associated with fd.
104 #include <stropts.h>
107 ...
108 int fd;
109 char *pathname = "/tmp/named-STREAM";
110 int ret;
111 ret = fattach(fd, pathname);
113
115 The fattach() function behaves similarly to the traditional mount()
116 function in the way a file is temporarily replaced by the root direc‐
117 tory of the mounted file system. In the case of fattach(), the replaced
118 file need not be a directory and the replacing file is a STREAMS file.
119
121 The file attributes of a file which has been the subject of an fat‐
122 tach() call are specifically set because of an artifact of the original
123 implementation. The internal mechanism was the same as for the mount()
124 function. Since mount() is typically only applied to directories, the
125 effects when applied to a regular file are a little surprising, espe‐
126 cially as regards the link count which rigidly remains one, even if
127 there were several links originally and despite the fact that all orig‐
128 inal links refer to the STREAM as long as the fattach() remains in
129 effect.
130
132 The fattach() function may be removed in a future version.
133
135 fdetach(), isastream()
136 The Base Definitions volume of POSIX.1‐2017, <stropts.h>
138
140 Portions of this text are reprinted and reproduced in electronic form
141 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
142 table Operating System Interface (POSIX), The Open Group Base Specifi‐
143 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
144 Electrical and Electronics Engineers, Inc and The Open Group. In the
145 event of any discrepancy between this version and the original IEEE and
146 The Open Group Standard, the original IEEE and The Open Group Standard
147 is the referee document. The original Standard can be obtained online
148 at http://www.opengroup.org/unix/online.html .
149 Any typographical or formatting errors that appear in this page are
151 most likely to have been introduced during the conversion of the source
152 files to man page format. To report such errors, see https://www.ker‐
153 nel.org/doc/man-pages/reporting_bugs.html .
154IEEE/The Open Group 2017 FATTACH(3P)