rget.1

来自「minix操作系统最新版本（3.1.1）的源代码」· 1 代码 · 共 170 行

.TH RGET 1
.SH NAME
rget, rput \- network pipe
.SH SYNOPSIS
.B rget
.RB [ \-lcio ]
.RB [ \-h
.IR host ]
.I key
.RI [ command
.RI [ arg " ...]]"
.br
.B rput
.RB [ \-lcio ]
.RB [ \-h
.IR host ]
.I key
.RI [ command
.RI [ arg " ...]]"
.SH DESCRIPTION
.de SP
.if t .sp 0.4
.if n .sp
..
.de XS	\" Example start
.SP
.in +4m
.nf
..
.de XE	\" Example end
.fi
.in -4m
.SP
..
.B Rput
and
.B rget
set up a TCP/IP channel to connect two processes together.  They can looked
upon as a remote pipe.  Consider the well known method of copying a
directory tree with
.BR tar :
.XS
(cd src && tar cf \- .) | (cd dst && tar xfp \-)
.XE
If the directory tree is to be copied to another machine then one can
use the following command on the source machine:
.XS
cd src && rput foo tar cf \- .
.XE
And on the destination machine:
.XS
cd dst && rget \-h \fIsource-machine\fP foo tar xfp \-
.XE
The
.I key
is either a port number in C style decimal, octal or hex, or a random string
that is hashed to a port number.
.B Rput
uses this port number to open a TCP socket that
.B rget
using the same
.I key
can connect to.
It is customary to start
.B rput
first, although
.B rget
will retry for 2 minutes trying to connect to the remote
.BR rput.
.PP
After the connection is established either utility will execute
.I command
with the given arguments with the TCP channel as either standard output
(rput) or standard input (rget).
.B Rput
and
.B rget
do not stay around for the command to finish, they simply overlay themselves
with the command.  If no command is given then they will themselves copy
standard input into the TCP channel (rput), or output from the TCP channel
to standard output (rget).  So these two commands have the same effect:
.XS
rput foo tar cf \- .
tar cf \- . | rput foo
.XE
The second form has two processes copying data instead of just
.B tar
directly writing its output into the TCP channel.  There is a better way to
waste processor cycles, namely to save bandwidth:
.XS
cd src && tar cf \- . | rput foo compress
.SP
cd dst && rget \-h \fIsource-machine\fP foo uncompress | tar xfp \-
.XE
.B Rput
and
.B rget
can be very useful in the windowed environments we use these days.  The
.B rput
can be typed into the window that has a shell running on one machine, and
the
.B rget
is then typed into the window that has a shell running on another machine.
This is easier than one of the two well known forms that use
.BR rsh :
.XS
cd src && tar cf \- . | rsh dest-machine "cd dst && tar xfp \-"
.SP
cd dst && rsh source-machine "cd src && tar cf \- ." | tar xfp \-
.XE
Especially since these forms require that one must be able to use
.B rsh
without a password, which may not always be the case.
.PP
The
.I key
can be any string of characters of any length.  If its a number then it is
used directly as the port number.  Otherwise the characters binary values
are multiplied together, bit 15 is set and the result is truncated to 16
bits to make it a port number in the anonymous port space (32768 \- 65535).
The port may be in-use on the source machine, but there is a small chance
of this happening, and if so simply choose another key.  (So if you use
.B rput
and
.B rget
in an unattended script then you should reserve a port number, otherwise
a connection can't be guaranteed.)
.SH OPTIONS
.TP
.B \-lcio
These flags allow one to reverse the default connect/listen or input/output
direction of
.BR rput
and
.BR rget .
Reversing the connection may be necessary if one of the two systems filters
out connections to unknown ports.  For example:
.XS
rput \-c \-h \fIdestination-machine\fP foo tar cf \- .
.SP
rget \-l foo tar xfp \-
.XE
The
.B \-io
options can be used to choose which of standard input or output should be
tied to the socket.  It's even possible to tie both input and output to the
socket with
.BR \-io,
but only when executing a command.  This is probably the only use for these
options, because one usually chooses the direction with the mnemonic put/get
names.
.TP
.BI \-h " host"
The name of the remote host that a connection must be made to.  It must be
used with the program that is doing the connect, usually
.BR rget .
This option is currently mandatory.  The author is planning to increase
ease of use by letting the programs find each other with UDP broadcasts
or multicasts.
.SH "SEE ALSO"
.BR rsh (1).
.SH DIAGNOSTICS
.TP 5
rput: Address in use
If the port computed out of
.I key
is already in use.
.SH AUTHOR
Kees J. Bot <[e-mail]>