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GETPEEREID(3)            BSD Library Functions Manual            GETPEEREID(3)

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

LIBRARY
     Standard C Library (libc, -lc)

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

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

DESCRIPTION
     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) or listen(2) have been called.  The effective used ID is placed in euid, and the
     effective group ID in egid.

     The credentials returned to the listen(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 listen(2).  This mechanism is reliable; there is no way for either side to influence the creden-tials credentials
     tials returned to its peer except by calling the appropriate system call (i.e., either connect(2) or
     listen(2)) under different effective credentials.

     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.

IMPLEMENTATION NOTES
     On FreeBSD, getpeereid() is implemented in terms of the LOCAL_PEERCRED unix(4) socket option.

RETURN VALUES
     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.

ERRORS
     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) or listen(2) have been
                        called.

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

SEE ALSO
     connect(2), getpeername(2), getsockname(2), getsockopt(2), listen(2), unix(4)

HISTORY
     The getpeereid() function appeared in FreeBSD 4.6.

BSD                              July 15, 2001                             BSD