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extattr_list_link (2)
  • >> extattr_list_link (2) ( FreeBSD man: Системные вызовы )

  • BSD mandoc
     

    NAME

    
    
    extattr_get_fd
    
     
    extattr_set_fd
    
     
    extattr_delete_fd
    
     
    extattr_list_fd
    
     
    extattr_get_file
    
     
    extattr_set_file
    
     
    extattr_delete_file
    
     
    extattr_list_file
    
     
    extattr_get_link
    
     
    extattr_set_link
    
     
    extattr_delete_link
    
     
    extattr_list_link
    
     - system calls to manipulate VFS extended attributes
    
     
    

    LIBRARY

    Lb libc
    
     
    

    SYNOPSIS

       #include <sys/types.h>
       #include <sys/extattr.h>
    ssize_t extattr_get_fd (int fd int attrnamespace const char *attrname void *data size_t nbytes);
    int extattr_set_fd (int fd int attrnamespace const char *attrname const void *data size_t nbytes);
    int extattr_delete_fd (int fd int attrnamespace const char *attrname);
    ssize_t extattr_list_fd (int fd int attrnamespace void *data size_t nbytes);
    ssize_t extattr_get_file (const char *path int attrnamespace const char *attrname void *data size_t nbytes);
    int extattr_set_file (const char *path int attrnamespace const char *attrname const void *data size_t nbytes);
    int extattr_delete_file (const char *path int attrnamespace const char *attrname);
    ssize_t extattr_list_file (const char *path int attrnamespace void *data size_t nbytes);
    ssize_t extattr_get_link (const char *path int attrnamespace const char *attrname void *data size_t nbytes);
    int extattr_set_link (const char *path int attrnamespace const char *attrname const void *data size_t nbytes);
    int extattr_delete_link (const char *path int attrnamespace const char *attrname);
    ssize_t extattr_list_link (const char *path int attrnamespace void *data size_t nbytes);
     

    DESCRIPTION

    Named extended attributes are meta-data associated with vnodes representing files and directories. They exist as Qq Li name=value pairs within a set of namespaces.

    The extattr_get_file ();
    system call retrieves the value of the specified extended attribute into a buffer pointed to by Fa data of size Fa nbytes . The extattr_set_file ();
    system call sets the value of the specified extended attribute to the data described by Fa data . The extattr_delete_file ();
    system call deletes the extended attribute specified. The extattr_list_file ();
    returns a list of attributes present in the requested namespace. Each list entry consists of a single byte containing the length of the attribute name, followed by the attribute name. The attribute name is not terminated by ASCII 0 (nul). The extattr_get_file (,);
    and extattr_list_file ();
    calls consume the Fa data and Fa nbytes arguments in the style of read(2); extattr_set_file ();
    consumes these arguments in the style of write(2).

    If Fa data is NULL in a call to extattr_get_file ();
    and extattr_list_file ();
    then the size of defined extended attribute data will be returned, rather than the quantity read, permitting applications to test the size of the data without performing a read. The extattr_delete_link (,);
    extattr_get_link (,);
    and extattr_set_link ();
    system calls behave in the same way as their _file counterparts, except that they do not follow symlinks.

    The extattr_get_fd (,);
    extattr_set_fd (,);
    extattr_delete_fd (,);
    and extattr_list_fd (,);
    calls are identical to their Qq Li _file counterparts except for the first argument. The Qq Li _fd functions take a file descriptor, while the Qq Li _file functions take a path. Both arguments describe a file associated with the extended attribute that should be manipulated.

    The following arguments are common to all the system calls described here:

    Fa attrnamespace
    the namespace in which the extended attribute resides; see extattr(9)
    Fa attrname
    the name of the extended attribute

    Named extended attribute semantics vary by file system implementing the call. Not all operations may be supported for a particular attribute. Additionally, the format of the data in Fa data is attribute-specific.

    For more information on named extended attributes, please see extattr(9).  

    CAVEAT

    This interface is under active development, and as such is subject to change as applications are adapted to use it. Developers are discouraged from relying on its stability.  

    RETURN VALUES

    If successful, the extattr_get_file (,);
    extattr_set_file (,);
    and extattr_list_file ();
    calls return the number of bytes that were read or written from the Fa data , respectively, or if Fa data was NULL then extattr_get_file ();
    and extattr_list_file ();
    return the number of bytes available to read. If any of the calls are unsuccessful, the value -1 is returned and the global variable errno is set to indicate the error.

    Rv -std extattr_delete_file  

    ERRORS

    The following errors may be returned by the system calls themselves. Additionally, the file system implementing the call may return any other errors it desires.

    Bq Er EFAULT
    The Fa attrnamespace and Fa attrname arguments, or the memory range defined by Fa data and Fa nbytes point outside the process's allocated address space.
    Bq Er ENAMETOOLONG
    The attribute name was longer than EXTATTR_MAXNAMELEN

    The extattr_get_fd (,);
    extattr_set_fd (,);
    extattr_delete_fd (,);
    and extattr_list_fd ();
    system calls may also fail if:

    Bq Er EBADF
    The file descriptor referenced by Fa fd was invalid.

    Additionally, the extattr_get_file (,);
    extattr_set_file (,);
    and extattr_delete_file ();
    calls may also fail due to the following errors:

    Bq Er ENOATTR
    The requested attribute was not defined for this file.
    Bq Er ENOTDIR
    A component of the path prefix is not a directory.
    Bq Er ENAMETOOLONG
    A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
    Bq Er ENOENT
    A component of the path name that must exist does not exist.
    Bq Er EACCES
    Search permission is denied for a component of the path prefix.

     

    SEE ALSO

    extattr(3), getextattr(8), setextattr(8), extattr(9), VOP_GETEXTATTR9, VOP_SETEXTATTR9  

    HISTORY

    Extended attribute support was developed as part of the TrustedBSD Project, and introduced in Fx 5.0 . It was developed to support security extensions requiring additional labels to be associated with each file or directory.  

    BUGS

    In earlier versions of this API, passing an empty string for the attribute name to extattr_get_fd (,);
    extattr_get_file (,);
    or extattr_get_link ();
    would return the list of attributes defined for the target object. This interface has been deprecated in preference to using the explicit list API, and should not be used.


     

    Index

    NAME
    LIBRARY
    SYNOPSIS
    DESCRIPTION
    CAVEAT
    RETURN VALUES
    ERRORS
    SEE ALSO
    HISTORY
    BUGS


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