Link two directories


#include <sys/iofunc.h>

int iofunc_link( resmgr_context_t* ctp,
                 io_link_t* msg,
                 iofunc_attr_t* attr,
                 iofunc_attr_t* dattr,
                 struct _client_info* info );


A pointer to a resmgr_context_t structure that the resource-manager library uses to pass context information between functions.
A pointer to the io_link_t structure that contains the message that the resource manager received; see below.
A pointer to the iofunc_attr_t structure that describes the characteristics of the resource.
NULL, or a pointer to the iofunc_attr_t structure that describes the characteristics of the parent directory.
NULL, or a pointer to a _client_info structure that contains information about the client. For information about this structure, see ConnectClientInfo().



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


The iofunc_link() helper function links directory attr to dattr for context ctp. It's similar to the iofunc_open() function.

The iofunc_link() function checks to see if the client (described by the optional info structure) has access to open the resource (name passed in the msg structure). The attr structure describes the resource's attributes, and the optional dattr structure defines the attributes of the parent directory (i.e. if dattr isn't NULL, it implies that the resource identified by attr is being created within the directory specified by dattr).

You can pass the info argument as NULL, in which case iofunc_link() obtains the client information itself via a call to iofunc_client_info(). It is, of course, more efficient to get the client info once, rather than calling this function with NULL every time.

If you pass NULL in info, the function returns information about a client's connection in info, and an error constant.

io_link_t structure

The io_link_t structure holds the _IO_CONNECT message received by the resource manager:

typedef union {
    struct _io_connect                  connect;
    struct _io_connect_link_reply       link_reply;
    struct _io_connect_ftype_reply      ftype_reply;
} io_link_t;

This message structure is a union of an input message (coming to the resource manager), _io_connect, and two possible output or reply messages (going back to the client):

The reply includes the following additional information:

struct _io_resmgr_link_extra {
    uint32_t                            nd;
    int32_t                             pid;
    int32_t                             chid;
    uint32_t                            handle;
    uint32_t                            flags;
    uint32_t                            file_type;
    uint32_t                            reserved[2];

typedef union _io_link_extra {
    struct _msg_info              info;    /* EXTRA_LINK (from client) */
    void                          *ocb;    /* EXTRA_LINK (from resmgr functions) */
    char                          path[1]; /* EXTRA_SYMLINK */
    struct _io_resmgr_link_extra  resmgr;  /* EXTRA_RESMGR_LINK */
} io_link_extra_t;
A pointer to a _msg_info structure.


NULL was passed in attr and dattr.
A fault occurred when the kernel tried to access the info buffer.
The client process is no longer valid.
NULL was passed in info.
The group ID or owner ID didn't match.


QNX Neutrino

Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes

See also:

ConnectClientInfo(), iofunc_attr_t, iofunc_client_info(), iofunc_open(), _msg_info, resmgr_context_t

Writing a Resource Manager

Resource Managers chapter of Getting Started with QNX Neutrino