Xau  library:  XauFileName,  XauReadAuth,  XauLockAuth,  XauUnlockAuth,
   XauWriteAuth, XauDisposeAuth, XauGetAuthByAddr, XauGetBestAuthByAddr  -
   X authority database routines


   #include <X11/Xauth.h>

   typedef struct xauth {
           unsigned short  family;
           unsigned short  address_length;
           char    *address;
           unsigned short  number_length;
           char    *number;
           unsigned short  name_length;
           char    *name;
           unsigned short  data_length;
           char    *data;
   } Xauth;

   char *XauFileName (void);

   Xauth *XauReadAuth (FILE *auth_file);

   int XauWriteAuth (FILE *auth_file, Xauth *auth);

   Xauth *XauGetAuthByAddr (unsigned short family, unsigned short
          address_length, const char *address, unsigned short
          number_length, const char *number, unsigned short
          name_length, const char *name);

   Xauth *XauGetBestAuthByAddr (unsigned short family, unsigned short
          address_length, const char *address, unsigned short
          number_length, const char *number, int types_length,
          char **types, const int *type_lengths);

   int XauLockAuth (const char *file_name, int retries, int
          timeout, long dead);

   int XauUnlockAuth (const char *file_name);

   int XauDisposeAuth (Xauth *auth);


   XauFileName  generates  the  default  authorization  file name by first
   checking the XAUTHORITY environment variable if set,  else  it  returns
   $HOME/.Xauthority.  This name is statically allocated and should not be

   XauReadAuth reads the next entry from  auth_file.   The  entry  is  not
   statically allocated and should be freed by calling XauDisposeAuth.

   XauWriteAuth  writes an authorization entry to auth_file.  It returns 1
   on success, 0 on failure.

   XauGetAuthByAddr searches for an entry which matches the given  network
   address/display number pair.  The entry is not statically allocated and
   should be freed by calling XauDisposeAuth.

   XauGetBestAuthByAddr is similar to XauGetAuthByAddr, except that a list
   of acceptable authentication methods is specified.  Xau will choose the
   file entry which matches the earliest entry in  this  list  (e.g.,  the
   most  secure authentication method).  The types argument is an array of
   strings, one  string  for  each  authentication  method.   types_length
   specifies  how  many elements are in the types array.  types_lengths is
   an array of integers representing the length of each string.

   XauLockAuth  does  the  work  necessary  to  synchronously  update   an
   authorization  file.   First  it  makes two file names, one with ``-c''
   appended to file_name, the other with ``-l'' appended.  If  the  ``-c''
   file  already  exists  and  is  more than dead seconds old, XauLockAuth
   removes it  and  the  associated  ``-l''  file.   To  prevent  possible
   synchronization  troubles  with  NFS,  a  dead value of zero forces the
   files to be removed.  XauLockAuth makes retries attempts to create  and
   link  the  file  names,  pausing  timeout seconds between each attempt.
   XauLockAuth returns a collection of values depending on the results:

          A system error occurred, either a file_name which is  too  long,
          or  an  unexpected  failure from a system call.  errno may prove

          retries attempts failed

          The lock succeeded.

   XauUnlockAuth undoes the work of  XauLockAuth  by  unlinking  both  the
   ``-c'' and ``-l'' file names.

   XauDisposeAuth frees storage allocated to hold an authorization entry.


   xauth(1), xdm(1)


   Keith Packard, MIT X Consortium


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