.\" $OpenBSD: getsockname.2,v 1.16 2001/08/06 10:42:26 mpech Exp $
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.\" $OpenBSD: getsockname.2,v 1.16 2001/08/06 10:42:26 mpech Exp $
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.\" $NetBSD: getsockname.2,v 1.6 1995/10/12 15:41:00 jtc Exp $
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.\" $NetBSD: getsockname.2,v 1.6 1995/10/12 15:41:00 jtc Exp $
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.\"
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\" without specific prior written permission.
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.\"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\" SUCH DAMAGE.
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.\"
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.\"
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.\" @(#)getsockname.2 8.1 (Berkeley) 6/4/93
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.\" @(#)getsockname.2 8.1 (Berkeley) 6/4/93
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.\"
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.\"
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.Dd July 17, 1999
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.Dd July 17, 1999
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.Dt GETSOCKNAME 2
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.Dt GETSOCKNAME 2
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.Os
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.Os
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.Sh NAME
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.Sh NAME
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.Nm getsockname
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.Nm getsockname
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.Nd get socket name
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.Nd get socket name
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.Sh SYNOPSIS
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.Sh SYNOPSIS
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.Fd #include
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.Fd #include
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.Fd #include
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.Fd #include
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.Ft int
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.Ft int
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.Fn getsockname "int s" "struct sockaddr *name" "socklen_t *namelen"
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.Fn getsockname "int s" "struct sockaddr *name" "socklen_t *namelen"
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.Sh DESCRIPTION
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.Sh DESCRIPTION
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.Fn getsockname
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.Fn getsockname
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returns the locally bound address information for a specified socket.
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returns the locally bound address information for a specified socket.
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.Pp
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.Pp
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Common uses of this function are as follows:
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Common uses of this function are as follows:
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.Bl -bullet
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.Bl -bullet
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.It
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.It
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When
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When
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.Xr bind 2
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.Xr bind 2
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is called with a port number of 0 (indicating the kernel should pick
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is called with a port number of 0 (indicating the kernel should pick
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an ephemeral port)
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an ephemeral port)
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.Fn getsockname
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.Fn getsockname
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is used to retrieve the kernel-assigned port number.
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is used to retrieve the kernel-assigned port number.
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.It
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.It
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When a process calls
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When a process calls
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.Xr bind 2
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.Xr bind 2
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on a wildcard IP address,
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on a wildcard IP address,
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.Fn getsockname
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.Fn getsockname
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is used to retrieve the local IP address for the connection.
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is used to retrieve the local IP address for the connection.
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.It
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.It
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When a function wishes to know the address family of a socket,
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When a function wishes to know the address family of a socket,
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.Fn getsockname
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.Fn getsockname
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can be used.
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can be used.
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.El
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.El
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.Pp
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.Pp
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.Fn getsockname
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.Fn getsockname
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takes three parameters:
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takes three parameters:
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.Pp
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.Pp
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.Fa s ,
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.Fa s ,
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Contains the file desriptor for the socket to be looked up.
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Contains the file desriptor for the socket to be looked up.
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.Pp
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.Pp
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.Fa name
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.Fa name
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points to a
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points to a
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.Li sockaddr
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.Li sockaddr
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structure which will hold the resulting address information.
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structure which will hold the resulting address information.
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Normal use requires one to use a structure
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Normal use requires one to use a structure
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specific to the protocol family in use, such as
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specific to the protocol family in use, such as
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.Li sockaddr_in
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.Li sockaddr_in
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(IPv4) or
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(IPv4) or
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.Li sockaddr_in6
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.Li sockaddr_in6
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(IPv6), cast to a (struct sockaddr *).
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(IPv6), cast to a (struct sockaddr *).
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.Pp
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.Pp
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For greater portability (such as newer protocol families) the new
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For greater portability (such as newer protocol families) the new
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structure sockaddr_storage exists.
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structure sockaddr_storage exists.
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.Li sockaddr_storage
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.Li sockaddr_storage
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is large enough to hold any of the other sockaddr_* variants.
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is large enough to hold any of the other sockaddr_* variants.
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On return, it should be cast to the correct sockaddr type,
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On return, it should be cast to the correct sockaddr type,
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according to the current protocol family.
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according to the current protocol family.
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.Pp
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.Pp
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.Fa namelen
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.Fa namelen
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Indicates the amount of space pointed to by
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Indicates the amount of space pointed to by
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.Fa name ,
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.Fa name ,
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in bytes.
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in bytes.
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Upon return,
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Upon return,
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.Fa namelen
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.Fa namelen
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is set to the actual size of the returned address information.
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is set to the actual size of the returned address information.
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.Pp
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.Pp
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If the address of the destination socket for a given socket connection is
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If the address of the destination socket for a given socket connection is
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needed, the
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needed, the
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.Xr getpeername 2
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.Xr getpeername 2
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function should be used instead.
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function should be used instead.
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.Pp
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.Pp
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If
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If
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.Fa name
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.Fa name
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does not point to enough space to hold the entire socket address, the
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does not point to enough space to hold the entire socket address, the
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result will be truncated to
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result will be truncated to
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.Fa namelen
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.Fa namelen
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bytes.
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bytes.
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.Sh RETURN VALUES
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.Sh RETURN VALUES
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On success,
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On success,
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.Fn getsockname
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.Fn getsockname
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returns a 0, and
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returns a 0, and
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.Fa namelen
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.Fa namelen
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is set to the actual size of the socket address returned in
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is set to the actual size of the socket address returned in
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.Fa name .
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.Fa name .
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Otherwise,
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Otherwise,
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.Va errno
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.Va errno
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is set, and a value of \-1 is returned.
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is set, and a value of \-1 is returned.
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.Sh ERRORS
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.Sh ERRORS
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If
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If
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.Fn getsockname
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.Fn getsockname
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fails,
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fails,
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.Va errno
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.Va errno
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is set to one of the following:
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is set to one of the following:
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.Bl -tag -width Er
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.Bl -tag -width Er
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.It Bq Er EBADF
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.It Bq Er EBADF
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The argument
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The argument
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.Fa s
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.Fa s
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is not a valid descriptor.
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is not a valid descriptor.
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.It Bq Er ENOTSOCK
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.It Bq Er ENOTSOCK
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The argument
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The argument
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.Fa s
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.Fa s
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is a file, not a socket.
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is a file, not a socket.
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.It Bq Er ENOBUFS
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.It Bq Er ENOBUFS
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Insufficient resources were available in the system
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Insufficient resources were available in the system
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to perform the operation.
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to perform the operation.
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.It Bq Er EFAULT
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.It Bq Er EFAULT
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The
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The
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.Fa name
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.Fa name
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parameter points to memory not in a valid part of the
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parameter points to memory not in a valid part of the
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process address space.
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process address space.
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.El
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.El
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.Sh SEE ALSO
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.Sh SEE ALSO
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.Xr accept 2 ,
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.Xr accept 2 ,
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.Xr bind 2 ,
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.Xr bind 2 ,
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.Xr getpeername 2 ,
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.Xr getpeername 2 ,
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.Xr getpeereid 2 ,
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.Xr getpeereid 2 ,
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.Xr socket 2
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.Xr socket 2
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.Sh BUGS
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.Sh BUGS
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Names bound to sockets in the UNIX domain are inaccessible;
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Names bound to sockets in the UNIX domain are inaccessible;
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.Nm getsockname
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.Nm getsockname
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returns a zero length name.
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returns a zero length name.
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.Sh HISTORY
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.Sh HISTORY
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The
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The
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.Fn getsockname
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.Fn getsockname
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function call appeared in
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function call appeared in
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.Bx 4.2 .
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.Bx 4.2 .
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