The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


bind - bind a name to a socket


#include <sys/socket.h>

int bind(int socket, const struct sockaddr *address,
     socklen_t address_len);


The bind() function assigns an address to an unnamed socket. Sockets created with socket() function are initially unnamed; they are identified only by their address family.

The function takes the following arguments:

Specifies the file descriptor of the socket to be bound.
Points to a sockaddr structure containing the address to be bound to the socket. The length and format of the address depend on the address family of the socket.
Specifies the length of the sockaddr structure pointed to by the address argument.

The socket in use may require the process to have appropriate privileges to use the bind() function.


Upon successful completion, bind() returns 0. Otherwise, -1 is returned and errno is set to indicate the error.


The bind() function will fail if:
The specified address is already in use.
The specified address is not available from the local machine.
The specified address is not a valid address for the address family of the specified socket.
The socket argument is not a valid file descriptor.
The address argument can not be accessed.
The socket is already bound to an address, and the protocol does not support binding to a new address; or the socket has been shut down.
The socket argument does not refer to a socket.
The socket type of the specified socket does not support binding to an address.

If the address family of the socket is AF_UNIX, then bind() will fail if:

A component of the path prefix denies search permission, or the requested name requires writing in a directory with a mode that denies write permission.

The address argument is a null pointer.
An I/O error occurred.
Too many symbolic links were encountered in translating the pathname in address.
A component of a pathname exceeded {NAME_MAX} characters, or an entire pathname exceeded {PATH_MAX} characters.
A component of the pathname does not name an existing file or the pathname is an empty string.
A component of the path prefix of the pathname in address is not a directory.
The name would reside on a read-only filesystem.

The bind() function may fail if:

The specified address is protected and the current user does not have permission to bind to it.
The address_len argument is not a valid length for the address family.
The socket is already connected.
Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.
Insufficient resources were available to complete the call.
There were insufficient STREAMS resources for the operation to complete.


An application program can retrieve the assigned socket name with the getsockname() function.


connect(), getsockname(), listen(), socket(), <sys/socket.h>.

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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