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diff --git a/man-pages-posix-2017/man3p/recvfrom.3p b/man-pages-posix-2017/man3p/recvfrom.3p new file mode 100644 index 0000000..3e427a7 --- /dev/null +++ b/man-pages-posix-2017/man3p/recvfrom.3p @@ -0,0 +1,245 @@ +'\" et +.TH RECVFROM "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" +.SH PROLOG +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. +.\" +.SH NAME +recvfrom +\(em receive a message from a socket +.SH SYNOPSIS +.LP +.nf +#include <sys/socket.h> +.P +ssize_t recvfrom(int \fIsocket\fP, void *restrict \fIbuffer\fP, size_t \fIlength\fP, + int \fIflags\fP, struct sockaddr *restrict \fIaddress\fP, + socklen_t *restrict \fIaddress_len\fP); +.fi +.SH DESCRIPTION +The +\fIrecvfrom\fR() +function shall receive a message from a connection-mode or +connectionless-mode socket. It is normally used with +connectionless-mode sockets because it permits the application to +retrieve the source address of received data. +.P +The +\fIrecvfrom\fR() +function takes the following arguments: +.IP "\fIsocket\fR" 12 +Specifies the socket file descriptor. +.IP "\fIbuffer\fR" 12 +Points to the buffer where the message should be stored. +.IP "\fIlength\fR" 12 +Specifies the length in bytes of the buffer pointed to by the +.IR buffer +argument. +.IP "\fIflags\fR" 12 +Specifies the type of message reception. Values of this argument are +formed by logically OR'ing zero or more of the following values: +.RS 12 +.IP MSG_PEEK 12 +Peeks at an incoming message. The data is treated as unread and the +next +\fIrecvfrom\fR() +or similar function shall still return this data. +.IP MSG_OOB 12 +Requests out-of-band data. The significance and semantics of +out-of-band data are protocol-specific. +.IP MSG_WAITALL 12 +On SOCK_STREAM sockets this requests that the function block until the +full amount of data can be returned. The function may return the +smaller amount of data if the socket is a message-based socket, if a +signal is caught, if the connection is terminated, if MSG_PEEK was +specified, or if an error is pending for the socket. +.RE +.IP "\fIaddress\fR" 12 +A null pointer, or points to a +.BR sockaddr +structure in which the sending address is to be stored. The length and +format of the address depend on the address family of the socket. +.IP "\fIaddress_len\fR" 12 +Either a null pointer, if +.IR address +is a null pointer, or a pointer to a +.BR socklen_t +object which on input specifies the length of the supplied +.BR sockaddr +structure, and on output specifies the length of the stored address. +.P +The +\fIrecvfrom\fR() +function shall return the length of the message written to the buffer +pointed to by the +.IR buffer +argument. For message-based sockets, such as +SOCK_RAW, +SOCK_DGRAM, and SOCK_SEQPACKET, the entire message shall be read in a +single operation. If a message is too long to fit in the supplied +buffer, and MSG_PEEK is not set in the +.IR flags +argument, the excess bytes shall be discarded. For stream-based +sockets, such as SOCK_STREAM, message boundaries shall be ignored. In +this case, data shall be returned to the user as soon as it becomes +available, and no data shall be discarded. +.P +If the MSG_WAITALL flag is not set, data shall be returned only up to +the end of the first message. +.P +Not all protocols provide the source address for messages. If the +.IR address +argument is not a null pointer and the protocol provides the source +address of messages, the source address of the received message shall +be stored in the +.BR sockaddr +structure pointed to by the +.IR address +argument, and the length of this address shall be stored in the object +pointed to by the +.IR address_len +argument. +.P +If the actual length of the address is greater than the length of the +supplied +.BR sockaddr +structure, the stored address shall be truncated. +.P +If the +.IR address +argument is not a null pointer and the protocol does not provide the +source address of messages, the value stored in the object pointed to +by +.IR address +is unspecified. +.P +If no messages are available at the socket and O_NONBLOCK is not set on +the socket's file descriptor, +\fIrecvfrom\fR() +shall block until a message arrives. If no messages are available at +the socket and O_NONBLOCK is set on the socket's file descriptor, +\fIrecvfrom\fR() +shall fail and set +.IR errno +to +.BR [EAGAIN] +or +.BR [EWOULDBLOCK] . +.SH "RETURN VALUE" +Upon successful completion, +\fIrecvfrom\fR() +shall return the length of the message in bytes. If no messages are +available to be received and the peer has performed an orderly +shutdown, +\fIrecvfrom\fR() +shall return 0. Otherwise, the function shall return \-1 and set +.IR errno +to indicate the error. +.SH ERRORS +The +\fIrecvfrom\fR() +function shall fail if: +.TP +.BR EAGAIN " or " EWOULDBLOCK +.br +The socket's file descriptor is marked O_NONBLOCK and no data is +waiting to be received; or MSG_OOB is set and no out-of-band data is +available and either the socket's file descriptor is marked O_NONBLOCK +or the socket does not support blocking to await out-of-band data. +.TP +.BR EBADF +The +.IR socket +argument is not a valid file descriptor. +.TP +.BR ECONNRESET +A connection was forcibly closed by a peer. +.TP +.BR EINTR +A signal interrupted +\fIrecvfrom\fR() +before any data was available. +.TP +.BR EINVAL +The MSG_OOB flag is set and no out-of-band data is available. +.TP +.BR ENOTCONN +A receive is attempted on a connection-mode socket that is not connected. +.TP +.BR ENOTSOCK +The +.IR socket +argument does not refer to a socket. +.TP +.BR EOPNOTSUPP +The specified flags are not supported for this socket type. +.TP +.BR ETIMEDOUT +The connection timed out during connection establishment, or due to a +transmission timeout on active connection. +.P +The +\fIrecvfrom\fR() +function may fail if: +.TP +.BR EIO +An I/O error occurred while reading from or writing to the file +system. +.TP +.BR ENOBUFS +Insufficient resources were available in the system to perform the +operation. +.TP +.BR ENOMEM +Insufficient memory was available to fulfill the request. +.LP +.IR "The following sections are informative." +.SH "EXAMPLES" +None. +.SH "APPLICATION USAGE" +The +\fIselect\fR() +and +\fIpoll\fR() +functions can be used to determine when data is available to be +received. +.SH "RATIONALE" +None. +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.IR "\fIpoll\fR\^(\|)", +.IR "\fIpselect\fR\^(\|)", +.IR "\fIread\fR\^(\|)", +.IR "\fIrecv\fR\^(\|)", +.IR "\fIrecvmsg\fR\^(\|)", +.IR "\fIsend\fR\^(\|)", +.IR "\fIsendmsg\fR\^(\|)", +.IR "\fIsendto\fR\^(\|)", +.IR "\fIshutdown\fR\^(\|)", +.IR "\fIsocket\fR\^(\|)", +.IR "\fIwrite\fR\^(\|)" +.P +The Base Definitions volume of POSIX.1\(hy2017, +.IR "\fB<sys_socket.h>\fP" +.\" +.SH COPYRIGHT +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 . +.PP +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 . |