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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of
this interface may differ (consult the corresponding Linux manual page for details of
Linux behavior), or the interface may not be implemented on Linux.
NAME
bind — bind a name to a socket
SYNOPSIS
#include <sys/socket.h>
int bind(int socket, const struct sockaddr *address,
socklen_t address_len);
DESCRIPTION
The bind() function shall assign a local socket address address to a socket identified by
descriptor socket that has no local socket address assigned. Sockets created with the
socket() function are initially unnamed; they are identified only by their address family.
The bind() function takes the following arguments:
socket Specifies the file descriptor of the socket to be bound.
address 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.
address_len Specifies the length of the sockaddr structure pointed to by the address
argument.
The socket specified by socket may require the process to have appropriate privileges to
use the bind() function.
If the address family of the socket is AF_UNIX and the pathname in address names a
symbolic link, bind() shall fail and set errno to [EADDRINUSE].
If the socket address cannot be assigned immediately and O_NONBLOCK is set for the file
descriptor for the socket, bind() shall fail and set errno to [EINPROGRESS], but the
assignment request shall not be aborted, and the assignment shall be completed
asynchronously. Subsequent calls to bind() for the same socket, before the assignment is
completed, shall fail and set errno to [EALREADY].
When the assignment has been performed asynchronously, pselect(), select(), and poll()
shall indicate that the file descriptor for the socket is ready for reading and writing.
RETURN VALUE
Upon successful completion, bind() shall return 0; otherwise, -1 shall be returned and
errno set to indicate the error.
ERRORS
The bind() function shall fail if:
EADDRINUSE
The specified address is already in use.
EADDRNOTAVAIL
The specified address is not available from the local machine.
EAFNOSUPPORT
The specified address is not a valid address for the address family of the
specified socket.
EALREADY
An assignment request is already in progress for the specified socket.
EBADF The socket argument is not a valid file descriptor.
EINPROGRESS
O_NONBLOCK is set for the file descriptor for the socket and the assignment cannot
be immediately performed; the assignment shall be performed asynchronously.
EINVAL 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.
ENOBUFS
Insufficient resources were available to complete the call.
ENOTSOCK
The socket argument does not refer to a socket.
EOPNOTSUPP
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() shall fail if:
EACCES 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.
EDESTADDRREQ or EISDIR
The address argument is a null pointer.
EIO An I/O error occurred.
ELOOP A loop exists in symbolic links encountered during resolution of the pathname in
address.
ENAMETOOLONG
The length of a component of a pathname is longer than {NAME_MAX}.
ENOENT A component of the path prefix of the pathname in address does not name an existing
file or the pathname is an empty string.
ENOENT or ENOTDIR
The pathname in address contains at least one non-<slash> character and ends with
one or more trailing <slash> characters. If the pathname without the trailing
<slash> characters would name an existing file, an [ENOENT] error shall not occur.
ENOTDIR
A component of the path prefix of the pathname in address names an existing file
that is neither a directory nor a symbolic link to a directory, or the pathname in
address contains at least one non-<slash> character and ends with one or more
trailing <slash> characters and the last pathname component names an existing file
that is neither a directory nor a symbolic link to a directory.
EROFS The name would reside on a read-only file system.
The bind() function may fail if:
EACCES The specified address is protected and the current user does not have permission to
bind to it.
EINVAL The address_len argument is not a valid length for the address family.
EISCONN
The socket is already connected.
ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the
pathname in address.
ENAMETOOLONG
The length of a pathname exceeds {PATH_MAX}, or pathname resolution of a symbolic
link produced an intermediate result with a length that exceeds {PATH_MAX}.
The following sections are informative.
EXAMPLES
The following code segment shows how to create a socket and bind it to a name in the
AF_UNIX domain.
#define MY_SOCK_PATH "/somepath"
int sfd;
struct sockaddr_un my_addr;
sfd = socket(AF_UNIX, SOCK_STREAM, 0);
if (sfd == -1)
/* Handle error */;
memset(&my_addr, '\0', sizeof(struct sockaddr_un));
/* Clear structure */
my_addr.sun_family = AF_UNIX;
strncpy(my_addr.sun_path, MY_SOCK_PATH, sizeof(my_addr.sun_path) -1);
if (bind(sfd, (struct sockaddr *) &my_addr,
sizeof(struct sockaddr_un)) == -1)
/* Handle error */;
APPLICATION USAGE
An application program can retrieve the assigned socket name with the getsockname()
function.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
connect(), getsockname(), listen(), socket()
The Base Definitions volume of POSIX.1‐2017, <sys_socket.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1-2017, Standard for Information Technology -- Portable Operating System Interface
(POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have
been introduced during the conversion of the source files to man page format. To report
such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .