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GETPEEREID(3)              Library Functions Manual              GETPEEREID(3)

     getpeereid - get the effective credentials of a UNIX-domain peer

     Standard C Library (libc, -lc)

     #include <sys/types.h>
     #include <unistd.h>

     getpeereid(int s, uid_t *euid, gid_t *egid);

     The getpeereid() function returns the effective user and group IDs of the
     peer connected to a UNIX-domain socket.  The argument s must be a
     UNIX-domain socket (unix(4)) of type SOCK_STREAM on which either
     connect(2) has been called, or one returned from accept(2) after bind(2)
     and listen(2) have been called.  If non-NULL, the effective used ID is
     placed in euid, and the effective group ID in egid.

     The credentials returned to the accept(2) caller are those of its peer at
     the time it called connect(2); the credentials returned to the connect(2)
     caller are those of its peer at the time it called bind(2).  This
     mechanism is reliable; there is no way for either side to influence the
     credentials returned to its peer except by calling the appropriate system
     call (i.e., either connect(2) or bind(2)) under different effective

     One common use of this routine is for a UNIX-domain server to verify the
     credentials of its client.  Likewise, the client can verify the
     credentials of the server.

     On NetBSD, getpeereid() is implemented in terms of the LOCAL_PEEREID
     unix(4) socket option.

     The getpeereid() function returns the value 0 if successful; otherwise
     the value -1 is returned and the global variable errno is set to indicate
     the error.

     The getpeereid() function fails if:

     [EBADF]            The argument s is not a valid descriptor.

     [ENOTSOCK]         The argument s is a file, not a socket.

     [ENOTCONN]         The argument s does not refer to a socket on which
                        connect(2) have been called nor one returned from

     [EINVAL]           The argument s does not refer to a socket of type
                        SOCK_STREAM, or the kernel returned invalid data.

     connect(2), getpeername(2), getsockname(2), getsockopt(2), listen(2),

     The getpeereid() function appeared in NetBSD 5.0.

NetBSD 9.99                     August 8, 2007                     NetBSD 9.99