GETPEEREID(3) BSD Library Functions Manual GETPEEREID(3)NAMEgetpeereid — get the effective credentials of a UNIX-domain peer
Standard C Library (libc, -lc)
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) 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 mech‐
anism is reliable; there is no way for either side to influence the cre‐
dentials returned to its peer except by calling the appropriate system
call (i.e., either connect(2) or listen(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 creden‐
tials of the server.
On FreeBSD, getpeereid() is implemented in terms of the LOCAL_PEERCRED
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 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 ALSOconnect(2), getpeername(2), getsockname(2), getsockopt(2), listen(2),
The getpeereid() function appeared in FreeBSD 4.6.
BSD July 15, 2001 BSD