getpeereid(3bsd) 3bsd getpeereid(3bsd)

# [NAME](#NAME)

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

# [LIBRARY](#LIBRARY)

library “libbsd”

# [SYNOPSIS](#SYNOPSIS)

`#include <sys/types.h>`  
`#include <unistd.h>` (See [libbsd(7)](/man/os/libbsd/libbsd.7) for include usage.)  
`int`  
`getpeereid`(`int s`, `uid_t *euid`, `gid_t *egid`);

# [DESCRIPTION](#DESCRIPTION)

The [`getpeereid`](#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)](/man/os/libbsd/unix.4)) of type `SOCK_STREAM` on which either [connect(2)](/man/os/libbsd/connect.2) or [listen(2)](/man/os/libbsd/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)](/man/os/libbsd/listen.2) caller are those of its peer at the time it called [connect(2)](/man/os/libbsd/connect.2); the credentials returned to the [connect(2)](/man/os/libbsd/connect.2) caller are those of its peer at the time it called [listen(2)](/man/os/libbsd/listen.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)](/man/os/libbsd/connect.2) or [listen(2)](/man/os/libbsd/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](#IMPLEMENTATION_NOTES)

On FreeBSD, `getpeereid`() is implemented in terms of the `LOCAL_PEERCRED` [unix(4)](/man/os/libbsd/unix.4) socket option.

# [RETURN VALUES](#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](#ERRORS)

The `getpeereid`() function fails if:

\[[`EBADF`](#EBADF)]

The argument `s` is not a valid descriptor.

\[[`ENOTSOCK`](#ENOTSOCK)]

The argument `s` is a file, not a socket.

\[[`ENOTCONN`](#ENOTCONN)]

The argument `s` does not refer to a socket on which [connect(2)](/man/os/libbsd/connect.2) or [listen(2)](/man/os/libbsd/listen.2) have been called.

\[[`EINVAL`](#EINVAL)]

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

# [SEE ALSO](#SEE_ALSO)

[connect(2)](/man/os/libbsd/connect.2), [getpeername(2)](/man/os/libbsd/getpeername.2), [getsockname(2)](/man/os/libbsd/getsockname.2), [getsockopt(2)](/man/os/libbsd/getsockopt.2), [listen(2)](/man/os/libbsd/listen.2), [unix(4)](/man/os/libbsd/unix.4)

# [HISTORY](#HISTORY)

The `getpeereid`() function appeared in FreeBSD 4.6, NetBSD 5.0 and OpenBSD 3.0.

July 15, 2001 Linux 4.19.0-gvisor

---

Document: getpeereid(3bsd) from libbsd 0.12.2-r11 (Chainguard OS)
Source: https://gitlab.freedesktop.org/libbsd/libbsd