---
name: "XAddHost"
section: "3x"
platform: "linux"
package: "libx11-dev"
version: "4.3.0.dfsg.1-14sarge7"
release: "Debian 3.1 (Sarge)"
platforms: ["linux"]
url: "https://new.carta.tech/XAddHost/3x"
---

# XAddHost(3x)

control host access and host control structure

## NAME

XAddHost, XAddHosts, XListHosts, XRemoveHost, XRemoveHosts, XSetAccessControl, XEnableAccessControl, XDisableAccessControl, XHostAddress - control host access and host control structure

## SYNTAX

int XAddHost(Display \**display*, XHostAddress \**host*);

int XAddHosts(Display \**display*, XHostAddress \**hosts*,  int *num\_hosts*);

XHostAddress \*XListHosts(Display \**display*, int \**nhosts\_return*, Bool *state\_return*);

int XRemoveHost(Display \**display*, XHostAddress \**host*);

int XRemoveHosts(Display \**display*, XHostAddress \**hosts*, int *num\_hosts*);

int XSetAccessControl(Display \**display*, int *mode*);

int XEnableAccessControl(Display \**display*);

int XDisableAccessControl(Display \**display*);

## ARGUMENTS

- *display*

  Specifies the connection to the X server.

- *host*

  Specifies the host that is to be added or removed.

- *hosts*

  Specifies each host that is to be added or removed.

- *mode*

  Specifies the mode. You can pass *EnableAccess* or *DisableAccess*.

- *nhosts\_return*

  Returns the number of hosts currently in the access control list.

- *num\_hosts*

  Specifies the number of hosts.

- *state\_return*

  Returns the state of the access control.

## DESCRIPTION

The *XAddHost* function adds the specified host to the access control list for that display. The server must be on the same host as the client issuing the command, or a *BadAccess* error results.

*XAddHost* can generate *BadAccess* and *BadValue* errors.

The *XAddHosts* function adds each specified host to the access control list for that display. The server must be on the same host as the client issuing the command, or a *BadAccess* error results.

*XAddHosts* can generate *BadAccess* and *BadValue* errors.

The *XListHosts* function returns the current access control list as well as whether the use  of the list at connection setup was enabled or disabled. *XListHosts* allows a program to find out what machines can make connections. It also returns a pointer to a list of host structures that were allocated by the function.  When no longer needed, this memory should be freed by calling *XFree*.

The *XRemoveHost* function removes the specified host from the access control list  for that display. The server must be on the same host as the client process, or a *BadAccess* error results. If you remove your machine from the access list, you can no longer connect to that server, and this operation cannot be reversed unless you reset the server.

*XRemoveHost* can generate *BadAccess* and *BadValue* errors.

The *XRemoveHosts* function removes each specified host from the access control list for that  display.   The X server must be on the same host as the client process, or a *BadAccess* error results. If you remove your machine from the access list,  you can no longer connect to that server, and this operation cannot be reversed unless you reset the server.

*XRemoveHosts* can generate *BadAccess* and *BadValue* errors.

The *XSetAccessControl* function either enables or disables the use of the access control list  at each connection setup.

*XSetAccessControl* can generate *BadAccess* and *BadValue* errors.

The *XEnableAccessControl* function enables the use of the access control list at each connection setup.

*XEnableAccessControl* can generate a *BadAccess* error.

The *XDisableAccessControl* function disables the use of the access control list at each connection setup.

*XDisableAccessControl* can generate a *BadAccess* error.

## STRUCTURES

The *XHostAddress* structure contains:

```
typedef struct {
	int family;
	int length;
	char *address;
} XHostAddress;

```

The family member specifies which protocol address family to use  (for example, TCP/IP or DECnet) and can be *FamilyInternet*, *FamilyDECnet*, or *FamilyChaos*. The length member specifies the length of the address in bytes. The address member specifies a pointer to the address.

## DIAGNOSTICS

- *BadAccess*

  A client attempted to modify the access control list from other than the local (or otherwise authorized) host.

- *BadValue*

  Some numeric value falls outside the range of values accepted by the request. Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted.  Any argument defined as a set of alternatives can generate this error.

## SEE ALSO

XFree(3X11)\
 *Xlib - C Language X Interface*