Xau(3) Library Functions Manual Xau(3)

# [NAME](#NAME)

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

# [SYNOPSIS](#SYNOPSIS)

```
#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);
```

# [DESCRIPTION](#DESCRIPTION)

**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 freed.

**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:

[LOCK\_ERROR](#LOCK_ERROR)

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

[LOCK\_TIMEOUT](#LOCK_TIMEOUT)

*retries* attempts failed

[LOCK\_SUCCESS](#LOCK_SUCCESS)

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.

# [SEE ALSO](#SEE_ALSO)

[xauth(1)](/man/os/libxau/xauth.1), [xdm(1)](/man/os/libxau/xdm.1)

# [AUTHOR](#AUTHOR)

Keith Packard, MIT X Consortium

libXau 1.0.12 X Version 11

---

Document: XauGetAuthByAddr(3) from libxau 1.0.12-r11 (Chainguard OS)
Source: https://gitlab.freedesktop.org/xorg/lib/libxau.git