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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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BIND(3P) POSIX Programmer's Manual BIND(3P)
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.
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 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.
Upon successful completion, bind() shall return 0; otherwise, -1
shall be returned and errno set to indicate the error.
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.
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 */;
An application program can retrieve the assigned socket name with
the getsockname() function.
None.
None.
connect(3p), getsockname(3p), listen(3p), socket(3p)
The Base Definitions volume of POSIX.1‐2017, sys_socket.h(0p)
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 .
IEEE/The Open Group 2017 BIND(3P)
Pages that refer to this page: netdb.h(0p), sys_socket.h(0p), sys_un.h(0p), accept(3p), connect(3p), getpeername(3p), getsockname(3p), getsockopt(3p), setsockopt(3p), socket(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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