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