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.\"     @(#)rexec.3     8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libcompat/4.3/rexec.3,v 1.12 2004/07/02 23:52:14 ru Exp $
.\"
.\" Taken from FreeBSD 5.4; not checked against Linux reality (mtk)
.\"
.\" 2013-06-21, mtk, Converted from mdoc to man macros
.\"
.TH REXEC 3 2014-05-28 "Linux" "Linux Programmer's Manual"
.SH NAME
rexec, rexec_af \- return stream to a remote command
.SH SYNOPSIS
.nf
.BR "#define _BSD_SOURCE" "             /* See feature_test_macros(7) */"
.B #include <netdb.h>
.sp
.BI "int rexec(char **" ahost ", int " inport ", const char *" user ", "
.BI "          const char *" passwd ", const char *" cmd ", int *" fd2p );
.sp
.BI "int rexec_af(char **" ahost ", int " inport ", const char *" user ", "
.BI "             const char *" passwd ", const char *" cmd ", int *" fd2p ,
.BI "             sa_family_t " af  );
.fi
.SH DESCRIPTION
This interface is obsoleted by
.BR rcmd (3).

The
.BR rexec ()
function
looks up the host
.IR *ahost
using
.BR gethostbyname (3),
returning \-1 if the host does not exist.
Otherwise,
.IR *ahost
is set to the standard name of the host.
If a username and password are both specified, then these
are used to authenticate to the foreign host; otherwise
the environment and then the
.I .netrc
file in user's
home directory are searched for appropriate information.
If all this fails, the user is prompted for the information.
.PP
The port
.I inport
specifies which well-known DARPA Internet port to use for
the connection; the call
.I "getservbyname(""exec"", ""tcp"")"
(see
.BR getservent (3))
will return a pointer to a structure that contains the necessary port.
The protocol for connection is described in detail in
.BR rexecd (8).
.PP
If the connection succeeds,
a socket in the Internet domain of type
.BR SOCK_STREAM
is returned to
the caller, and given to the remote command as
.IR stdin
and
.IR stdout .
If
.I fd2p
is nonzero, then an auxiliary channel to a control
process will be setup, and a descriptor for it will be placed
in
.IR *fd2p .
The control process will return diagnostic
output from the command (unit 2) on this channel, and will also
accept bytes on this channel as being UNIX signal numbers, to be
forwarded to the process group of the command.
The diagnostic
information returned does not include remote authorization failure,
as the secondary connection is set up after authorization has been
verified.
If
.I fd2p
is 0, then the
.IR stderr
(unit 2 of the remote
command) will be made the same as the
.IR stdout
and no
provision is made for sending arbitrary signals to the remote process,
although you may be able to get its attention by using out-of-band data.
.SS rexec_af()
The
.BR rexec ()
function works over IPv4
.RB ( AF_INET ).
By contrast, the
.BR rexec_af ()
function provides an extra argument,
.IR af ,
that allows the caller to select the protocol.
This argument can be specified as
.BR AF_INET ,
.BR AF_INET6 ,
or
.BR AF_UNSPEC
(to allow the implementation to select the protocol).
.SH VERSIONS
The
.BR rexec_af ()
function was added to glibc in version 2.2.
.SH ATTRIBUTES
.SS Multithreading (see pthreads(7))
The
.BR rexec ()
and
.BR rexec_af ()
functions are not thread-safe.
.SH CONFORMING TO
These functions are not in POSIX.1-2001.
The
.BR rexec ()
function first appeared in
4.2BSD, and is present on the BSDs, Solaris, and many other systems.
The
.BR rexec_af ()
function is more recent, and less widespread.
.SH BUGS
The
.BR rexec ()
function sends the unencrypted password across the network.
.PP
The underlying service is considered a big security hole and therefore
not enabled on many sites; see
.BR rexecd (8)
for explanations.
.SH SEE ALSO
.BR rcmd (3),
.BR rexecd (8)
.SH COLOPHON
This page is part of release 3.74 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%http://www.kernel.org/doc/man\-pages/.