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FATTACH(3P) POSIX Programmer's ManualFATTACH(3P)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.
fattach — attach a STREAMS-based file descriptor to a file in the file system name space (STREAMS)
#include <stropts.h> int fattach(intfildes, const char *path);
Thefattach() function shall attach a STREAMS-based file descriptor to a file, effectively associating a pathname withfildes. The application shall ensure that thefildes argument is a valid open file descriptor associated with a STREAMS file. Thepath argument points to a pathname of an existing file. The application shall have appropriate privileges or be the owner of the file named bypath and have write permission. A successful call tofattach() shall cause all pathnames that name the file named bypath to name the STREAMS file associated withfildes, 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. 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 bypath, the number of links is set to 1, and the size and device identifier are set to those of the STREAMS file associated withfildes. If any attributes of the named STREAMS file are subsequently changed (for example, bychmod()), neither the attributes of the underlying file nor the attributes of the STREAMS file to whichfildes refers shall be affected. File descriptors referring to the underlying file, opened prior to anfattach() call, shall continue to refer to the underlying file.
Upon successful completion,fattach() shall return 0. Otherwise, -1 shall be returned anderrno set to indicate the error.
Thefattach() function shall fail if:EACCESSearch permission is denied for a component of the path prefix, or the process is the owner ofpath but does not have write permissions on the file named bypath.EBADFThefildes argument is not a valid open file descriptor.EBUSYThe file named bypath is currently a mount point or has a STREAMS file attached to it.ELOOPA loop exists in symbolic links encountered during resolution of thepath argument.ENAMETOOLONG The length of a component of a pathname is longer than {NAME_MAX}.ENOENTA component ofpath does not name an existing file orpath is an empty string.ENOTDIR A component of the path prefix names an existing file that is neither a directory nor a symbolic link to a directory, or thepath argument contains at least one non-<slash> character and ends with one or more trailing <slash> characters.EPERMThe effective user ID of the process is not the owner of the file named bypath and the process does not have appropriate privileges. Thefattach() function may fail if:EINVALThefildes argument does not refer to a STREAMS file.ELOOPMore than {SYMLOOP_MAX} symbolic links were encountered during resolution of thepath argument.ENAMETOOLONG 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}.EXDEVA link to a file on another file system was attempted.The following sections are informative.Attaching a File Descriptor to a File In the following example,fd refers to an open STREAMS file. The call tofattach() associates this STREAM with the file/tmp/named-STREAM, such that any future calls to open/tmp/named-STREAM, prior to breaking the attachment via a call tofdetach(), will instead create a new file handle referring to the STREAMS file associated withfd. #include <stropts.h> ... int fd; char *pathname = "/tmp/named-STREAM"; int ret; ret = fattach(fd, pathname);
Thefattach() function behaves similarly to the traditionalmount() function in the way a file is temporarily replaced by the root directory of the mounted file system. In the case offattach(), the replaced file need not be a directory and the replacing file is a STREAMS file.
The file attributes of a file which has been the subject of anfattach() call are specifically set because of an artifact of the original implementation. The internal mechanism was the same as for themount() function. Sincemount() 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 thefattach() remains in effect.
Thefattach() function may be removed in a future version.
fdetach(3p),isastream(3p) The Base Definitions volume of POSIX.1‐2017,stropts.h(0p)
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 athttp://www.opengroup.org/unix/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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group 2017FATTACH(3P)Pages that refer to this page:stropts.h(0p), close(3p), fdetach(3p)
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