This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       When a connection is available, select() indicates that the file descriptor for the socket is  ready  for
       reading.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                        ACCEPT(3POSIX)

       The  accept()  function  shall extract the first connection on the queue of pending connections, create a
       new socket with the same socket type protocol and address family as the specified socket, and allocate  a
       new file descriptor for that socket. The file descriptor shall be allocated as described in Section2.14,
       FileDescriptorAllocation.

       The accept() function takes the following arguments:

       socket      Specifies  a socket that was created with socket(), has been bound to an address with bind(),
                   and has issued a successful call to listen().

       address     Either a null pointer, or a pointer  to  a  sockaddr  structure  where  the  address  of  the
                   connecting socket shall be returned.

       address_len Either a null pointer, if address is a null pointer, or a pointer to a socklen_t object which
                   on input specifies the length of the supplied sockaddr structure, and on output specifies the
                   length of the stored address.

       If  address is not a null pointer, the address of the peer for the accepted connection shall be stored in
       the sockaddr structure pointed to by address, and the length of this  address  shall  be  stored  in  the
       object pointed to by address_len.

       If  the  actual  length of the address is greater than the length of the supplied sockaddr structure, the
       stored address shall be truncated.

       If the protocol permits connections by unbound clients, and the peer is not bound, then the value  stored
       in the object pointed to by address is unspecified.

       If  the listen queue is empty of connection requests and O_NONBLOCK is not set on the file descriptor for
       the socket, accept() shall block until a connection is  present.  If  the  listen()  queue  is  empty  of
       connection  requests and O_NONBLOCK is set on the file descriptor for the socket, accept() shall fail and
       set errno to [EAGAIN] or [EWOULDBLOCK].

       The accepted socket cannot itself accept more connections. The  original  socket  remains  open  and  can
       accept more connections.

       The accept() function shall fail if:

       EAGAIN or EWOULDBLOCK
              O_NONBLOCK is set for the socket file descriptor and no connections are present to be accepted.

       EBADF  The socket argument is not a valid file descriptor.

       ECONNABORTED
              A connection has been aborted.

       EINTR  The  accept()  function  was  interrupted  by  a  signal that was caught before a valid connection
              arrived.

       EINVAL The socket is not accepting connections.

       EMFILE All file descriptors available to the process are currently open.

       ENFILE The maximum number of file descriptors in the system are already open.

       ENOBUFS
              No buffer space is available.

       ENOMEM There was insufficient memory available to complete the operation.

       ENOTSOCK
              The socket argument does not refer to a socket.

       EOPNOTSUPP
              The socket type of the specified socket does not support accepting connections.

       The accept() function may fail if:

       EPROTO A protocol error has occurred; for example, the STREAMS protocol stack has not been initialized.

       Thefollowingsectionsareinformative.

       None.

       None.

       accept — accept a new connection on a socket

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

       Upon  successful  completion,  accept()  shall  return  the  non-negative file descriptor of the accepted
       socket.  Otherwise, -1 shall be returned, errno shall be set  to  indicate  the  error,  and  any  object
       pointed to by address_len shall remain unchanged.

Section2.14, FileDescriptorAllocation, bind(), connect(), listen(), socket()

       The Base Definitions volume of POSIX.1‐2017, <sys_socket.h>

       #include <sys/socket.h>

       int accept(int socket, struct sockaddr *restrict address,
           socklen_t *restrict address_len);