pathmgr_link()

Create a link

Synopsis:

#include <pthread.h>

int pathmgr_link( const char *path,
                  uint32_t nd,
                  pid_t pid,
                  int chid,
                  unsigned handle,
                  enum _file_type file_type,
                  unsigned flags );

Arguments:

path

The path that you want to link to, or NULL to link to /.

nd

The node descriptor of the node (e.g., ND_LOCAL_NODE for the local node) of the process you want to associate the link with; see “Node descriptors,” below.

pid

The process ID to associate with the link, or 0 for the calling process.

chid

The channel ID to associate with the link.

handle

A handle to associate with the link.

file_type

The file type; one of the following (defined in <sys/ftype.h>):

• _FTYPE_ANY — the path name can be anything.
• _FTYPE_LINK — reserved for the process manager.
• _FTYPE_MOUNT — receive mount requests on the path (path must be NULL).
• _FTYPE_MQUEUE — reserved for a message-queue manager.
• _FTYPE_PIPE — reserved for a pipe manager.
• _FTYPE_SEM — reserved for a semaphore manager.
• _FTYPE_SHMEM — reserved for a shared memory object.
• _FTYPE_SOCKET — reserved for a socket manager.
• _FTYPE_SYMLINK — reserved for the Process Manager.

flags

0, or a combination of the following:

• PATHMGR_FLAG_BEFORE
• PATHMGR_FLAG_AFTER
• PATHMGR_FLAG_OPAQUE
• PATHMGR_FLAG_FTYPEONLY
• PATHMGR_FLAG_FTYPEALL
• PATHMGR_FLAG_STICKY
• PATHMGR_FLAG_DIR
• PATHMGR_FLAG_SELF

For more information, see “The flags argument,” below.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The pathmgr_link() function creates a link in the process manager. The nd, pid, chid, and handle together identify who handles the specified path; for more information, see “The client's view” in the Resource Managers chapter of Getting Started with QNX Neutrino.

You can use pathmgr_unlink() to remove the link.

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The link isn't permanent and is lost when the system reboots.

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The flags argument

The flags argument specifies additional information to control the pathname resolution:

PATHMGR_FLAG_AFTER

Force the path to be resolved after others with the same pathname at the same mountpoint.

PATHMGR_FLAG_BEFORE

Force the path to be resolved before others with the same pathname at the same mountpoint.

PATHMGR_FLAG_DIR

Treat the pathname as a directory and allow the resolving of longer pathnames. The _IO_CONNECT message contains the pathname passed to the client open() with the matching prefix stripped off. Without this flag, the pathname is treated as a simple file requiring an exact match.

Attached path	Opened path	PATHMGR_FLAG_DIR set	PATHMGR_FLAG_DIR clear
/a/b	/a/b	Match ""	Match ""
/a/b	/a/b/c	Match c	No match
/a/b	/a/b/c/d	Match c/d	No match
/a/b	/a/bc	No match	No match

You can't attach a directory pathname that contains, as a subset, an existing file pathname. Likewise, you can't attach a file pathname that's a subset of an existing directory pathname.

Existing path	New path	New path allowed?
Directory /a/b	Directory /a	Yes
Directory /a/b	Directory /a/b/c	Yes
File /a/b	Directory /a	Yes
File /a/b	Directory /a/b/c	No; the directory is beneath a file
Directory /a/b	File /a	No; the directory is beneath a file
Directory /a/b	File /a/b/c	Yes
File /a/b	File /a	Yes
File /a/b	File /a/b/c	Yes

PATHMGR_FLAG_FTYPEALL

Handle requests for all file types. You must specify a registration file type of _FTYPE_ALL.

PATHMGR_FLAG_FTYPEONLY

Handle only requests for the specific filetype indicated. The pathname must be NULL.

PATHMGR_FLAG_OPAQUE

Don't resolve paths to mountpoints on a path shorter than this (i.e. find the longest match against all pathnames attached).

PATHMGR_FLAG_SELF

Allow requests to resolve back to this server.

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Be very careful if you set PATHMGR_FLAG_SELF because it's possible for a deadlock to occur. For more information, see “Robust implementations with Send/Receive/Reply” in the Interprocess Communication (IPC) chapter of the System Architecture guide.

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PATHMGR_FLAG_STICKY

No ID is associated with the path. You must use pathmgr_unlink() to remove the link.

Node descriptors

The nd (node descriptor) is a temporary numeric description of a remote node. For more information, see the Qnet Networking chapter of the System Architecture guide.

Returns:

A unique ID for the link, or -1 if an error occurred (errno is set).

Classification:

QNX Neutrino

See also:

pathmgr_symlink(), pathmgr_unlink(), resmgr_attach()