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BIND(2)                    Linux Programmer's Manual                   BIND(2)

       bind - bind a name to a socket

       #include <sys/types.h>          /* See NOTES */
       #include <sys/socket.h>

       int bind(int sockfd, const struct sockaddr *addr,
                socklen_t addrlen);

       When a socket is created with socket(2), it exists in a name space (address family) but has no address assigned
       to it.  bind() assigns the address specified to by addr to the  socket  referred  to  by  the  file  descriptor
       sockfd.   addrlen  specifies  the  size, in bytes, of the address structure pointed to by addr.  Traditionally,
       this operation is called "assigning a name to a socket".

       It is normally necessary to assign a local address using bind() before a SOCK_STREAM socket may receive connec-
       tions (see accept(2)).

       The  rules  used  in  name  binding vary between address families.  Consult the manual entries in Section 7 for
       detailed information.  For AF_INET  see  ip(7),  for  AF_INET6  see  ipv6(7),  for  AF_UNIX  see  unix(7),  for
       AF_APPLETALK  see ddp(7), for AF_PACKET see packet(7), for AF_X25 see x25(7) and for AF_NETLINK see netlink(7).

       The actual structure passed for the addr argument will depend on the address family.  The sockaddr structure is
       defined as something like:

           struct sockaddr {
               sa_family_t sa_family;
               char        sa_data[14];

       The  only  purpose of this structure is to cast the structure pointer passed in addr in order to avoid compiler
       warnings.  See EXAMPLE below.

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

       EACCES The address is protected, and the user is not the superuser.

              The given address is already in use.

       EBADF  sockfd is not a valid descriptor.

       EINVAL The socket is already bound to an address.

              sockfd is a descriptor for a file, not a socket.

       The following errors are specific to Unix domain (AF_UNIX) sockets:

       EACCES Search permission is denied on a component of the path prefix.  (See also path_resolution(7).)

              A nonexistent interface was requested or the requested address was not local.

       EFAULT addr points outside the user's accessible address space.

       EINVAL The addrlen is wrong, or the socket was not in the AF_UNIX family.

       ELOOP  Too many symbolic links were encountered in resolving addr.

              addr is too long.

       ENOENT The file does not exist.

       ENOMEM Insufficient kernel memory was available.

              A component of the path prefix is not a directory.

       EROFS  The socket inode would reside on a read-only file system.

       SVr4, 4.4BSD, POSIX.1-2001 (bind() first appeared in 4.2BSD).

       POSIX.1-2001 does not require the inclusion of <sys/types.h>, and this header file is not  required  on  Linux.
       However,  some historical (BSD) implementations required this header file, and portable applications are proba-
       bly wise to include it.

       The third argument of bind() is in reality an int (and this is what 4.x BSD and libc4 and  libc5  have).   Some
       POSIX confusion resulted in the present socklen_t, also used by glibc.  See also accept(2).

       The transparent proxy options are not described.

       An example of the use of bind() with Internet domain sockets can be found in getaddrinfo(3).

       The following example shows how to bind a stream socket in the Unix (AF_UNIX) domain, and accept connections:

       #include <sys/socket.h>
       #include <sys/un.h>
       #include <stdlib.h>
       #include <stdio.h>
       #include <string.h>

       #define MY_SOCK_PATH "/somepath"
       #define LISTEN_BACKLOG 50

       #define handle_error(msg) \
           do { perror(msg); exit(EXIT_FAILURE); } while (0)

       main(int argc, char *argv[])
           int sfd, cfd;
           struct sockaddr_un my_addr, peer_addr;
           socklen_t peer_addr_size;

           sfd = socket(AF_UNIX, SOCK_STREAM, 0);
           if (sfd == -1)

           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)

           if (listen(sfd, LISTEN_BACKLOG) == -1)

           /* Now we can accept incoming connections one
              at a time using accept(2) */

           peer_addr_size = sizeof(struct sockaddr_un);
           cfd = accept(sfd, (struct sockaddr *) &peer_addr,
           if (cfd == -1)

           /* Code to deal with incoming connection(s)... */

           /* When no longer required, the socket pathname, MY_SOCK_PATH
              should be deleted using unlink(2) or remove(3) */

       accept(2),  connect(2),  getsockname(2),  listen(2),  socket(2), getaddrinfo(3), getifaddrs(3), ip(7), ipv6(7),
       path_resolution(7), socket(7), unix(7)

       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at

Linux                             2007-12-28                           BIND(2)