telnet.1

这是关于远程登陆TELNET 的源代码 已经测试过的。

.Dv FALSE
any of the specified variables.
The values of variables may be interrogated with the
.Ic display
command.
The variables which may be set or unset, but not toggled, are
listed here.  In addition, any of the variables for the
.Ic toggle
command may be explicitly set or unset.
.Bl -tag -width escape
.It Ic ayt
If
.Tn telnet
is in localchars mode, or
.Dv LINEMODE
is enabled, and the status character is typed, a
.Dv TELNET AYT
sequence is sent to the remote host.  The initial value for the "Are
You There" character is the terminal's status character.
.It Ic echo
This is the value (initially \*(Lq^E\*(Rq) which, when in
\*(Lqline by line\*(Rq mode, toggles between doing local echoing
of entered characters (for normal processing), and suppressing
echoing of entered characters (for entering, say, a password).
.It Ic eof
If
.Nm telnet
is operating in
.Dv LINEMODE
or \*(Lqold line by line\*(Rq mode, entering this character
as the first character on a line will cause this character to be
sent to the remote system.
The initial value of the eof character is taken to be the terminal's
.Ic eof
character.
.It Ic erase
If
.Nm telnet
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below),
.Sy and
if
.Nm telnet
is operating in \*(Lqcharacter at a time\*(Rq mode, then when this
character is typed, a
.Dv TELNET EC
sequence (see
.Ic send
.Ic ec
above)
is sent to the remote system.
The initial value for the erase character is taken to be
the terminal's
.Ic erase
character.
.It Ic escape
This is the
.Nm telnet
escape character (initially \*(Lq^[\*(Rq) which causes entry
into
.Nm telnet
command mode (when connected to a remote system).
.It Ic flushoutput
If
.Nm telnet
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below)
and the
.Ic flushoutput
character is typed, a
.Dv TELNET AO
sequence (see
.Ic send
.Ic ao
above)
is sent to the remote host.
The initial value for the flush character is taken to be
the terminal's
.Ic flush
character.
.It Ic forw1
.It Ic forw2
If
.Tn TELNET
is operating in
.Dv LINEMODE ,
these are the
characters that, when typed, cause partial lines to be
forwarded to the remote system.  The initial value for
the forwarding characters are taken from the terminal's
eol and eol2 characters.
.It Ic interrupt
If
.Nm telnet
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below)
and the
.Ic interrupt
character is typed, a
.Dv TELNET IP
sequence (see
.Ic send
.Ic ip
above)
is sent to the remote host.
The initial value for the interrupt character is taken to be
the terminal's
.Ic intr
character.
.It Ic kill
If
.Nm telnet
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below),
.Ic and
if
.Nm telnet
is operating in \*(Lqcharacter at a time\*(Rq mode, then when this
character is typed, a
.Dv TELNET EL
sequence (see
.Ic send
.Ic el
above)
is sent to the remote system.
The initial value for the kill character is taken to be
the terminal's
.Ic kill
character.
.It Ic lnext
If
.Nm telnet
is operating in
.Dv LINEMODE
or \*(Lqold line by line\*(Lq mode, then this character is taken to
be the terminal's
.Ic lnext
character.
The initial value for the lnext character is taken to be
the terminal's
.Ic lnext
character.
.It Ic quit
If
.Nm telnet
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below)
and the
.Ic quit
character is typed, a
.Dv TELNET BRK
sequence (see
.Ic send
.Ic brk
above)
is sent to the remote host.
The initial value for the quit character is taken to be
the terminal's
.Ic quit
character.
.It Ic reprint
If
.Nm telnet
is operating in
.Dv LINEMODE
or \*(Lqold line by line\*(Lq mode, then this character is taken to
be the terminal's
.Ic reprint
character.
The initial value for the reprint character is taken to be
the terminal's
.Ic reprint
character.
.It Ic rlogin
This is the rlogin mode escape character. Setting it enables rlogin
mode, as with the
.Ar r
command-line option (q.v.)
.It Ic start
If the
.Dv TELNET TOGGLE-FLOW-CONTROL
option has been enabled,
then this character is taken to
be the terminal's
.Ic start
character.
The initial value for the kill character is taken to be
the terminal's
.Ic start
character.
.It Ic stop
If the
.Dv TELNET TOGGLE-FLOW-CONTROL
option has been enabled,
then this character is taken to
be the terminal's
.Ic stop
character.
The initial value for the kill character is taken to be
the terminal's
.Ic stop
character.
.It Ic susp
If
.Nm telnet
is in
.Ic localchars
mode, or
.Dv LINEMODE
is enabled, and the
.Ic suspend
character is typed, a
.Dv TELNET SUSP
sequence (see
.Ic send
.Ic susp
above)
is sent to the remote host.
The initial value for the suspend character is taken to be
the terminal's
.Ic suspend
character.
.It Ic tracefile
This is the file to which the output, caused by
.Ic netdata
or
.Ic option
tracing being
.Dv TRUE ,
will be written.  If it is set to
.Dq Fl ,
then tracing information will be written to standard output (the default).
.It Ic worderase
If
.Nm telnet
is operating in
.Dv LINEMODE
or \*(Lqold line by line\*(Lq mode, then this character is taken to
be the terminal's
.Ic worderase
character.
The initial value for the worderase character is taken to be
the terminal's
.Ic worderase
character.
.It Ic \&?
Displays the legal
.Ic set
.Pq Ic unset
commands.
.El
.It Ic slc Ar state 
The
.Ic slc
command (Set Local Characters) is used to set
or change the state of the the special
characters when the 
.Dv TELNET LINEMODE
option has
been enabled.  Special characters are characters that get
mapped to 
.Tn TELNET
commands sequences (like
.Ic ip
or
.Ic quit  )
or line editing characters (like
.Ic erase
and
.Ic kill  ) .
By default, the local special characters are exported.
.Bl -tag -width Fl
.It Ic check
Verify the current settings for the current special characters.
The remote side is requested to send all the current special
character settings, and if there are any discrepancies with
the local side, the local side will switch to the remote value.
.It Ic export
Switch to the local defaults for the special characters.  The
local default characters are those of the local terminal at
the time when
.Nm telnet
was started.
.It Ic import
Switch to the remote defaults for the special characters.
The remote default characters are those of the remote system
at the time when the 
.Tn TELNET
connection was established.
.It Ic \&?
Prints out help information for the
.Ic slc
command.
.El
.It Ic status
Show the current status of
.Nm telnet .
This includes the name of the remote host, if any, as well as the
current mode.
.It Ic toggle Ar arguments ... 
Toggle (between
.Dv TRUE
and
.Dv FALSE )
various flags that control how
.Nm telnet
responds to events.
These flags may be set explicitly to
.Dv TRUE
or
.Dv FALSE
using the
.Ic set
and
.Ic unset
commands.
More than one flag may be toggled at once.
The state of these flags may be examined with the
.Ic display
command.
Valid flags are:
.Bl -tag -width Ar
.It Ic authdebug
Turns on debugging for the authentication code. This flag only exists
if authentication support is enabled.
.It Ic autoflush
If
.Ic autoflush
and
.Ic localchars
are both
.Dv TRUE ,
then when the
.Ic ao  ,
or
.Ic quit
characters are recognized (and transformed into
.Tn TELNET
sequences; see
.Ic set
above for details),
.Nm telnet
refuses to display any data on the user's terminal
until the remote system acknowledges (via a
.Dv TELNET TIMING MARK
option)
that it has processed those
.Tn TELNET
sequences.
The initial value for this toggle is
.Dv TRUE
if the terminal user had not
done an "stty noflsh", otherwise
.Dv FALSE
(see
.Xr stty  1  ) .
.It Ic autodecrypt
When the
.Dv TELNET ENCRYPT
option is negotiated, by
default the actual encryption (decryption) of the data
stream does not start automatically.  The autoencrypt
(autodecrypt) command states that encryption of the
output (input) stream should be enabled as soon as
possible.
.Pp
Note that this flag exists only if encryption support is enabled.
.It Ic autologin
If the remote side supports the
.Dv TELNET AUTHENTICATION
option,
.Tn telnet
attempts to use it to perform automatic authentication.  If the
.Dv TELNET AUTHENTICATION
option is not supported, the user's login name is propagated using the
.Dv TELNET ENVIRON
option.
Setting this flag is the same as specifying the
.Ar a
option to the
.Ic open
command or on the command line.
.It Ic autosynch
If
.Ic autosynch
and
.Ic localchars
are both
.Dv TRUE ,
then when either the
.Ic intr
or
.Ic quit
characters is typed (see
.Ic set
above for descriptions of the
.Ic intr
and
.Ic quit
characters), the resulting
.Tn telnet
sequence sent is followed by the
.Dv TELNET SYNCH
sequence.
This procedure
.Ic should
cause the remote system to begin throwing away all previously
typed input until both of the
.Tn telnet
sequences have been read and acted upon.
The initial value of this toggle is
.Dv FALSE .
.It Ic binary
Enable or disable the
.Dv TELNET BINARY
option on both input and output.
.It Ic inbinary
Enable or disable the
.Dv TELNET BINARY
option on input.
.It Ic outbinary
Enable or disable the
.Dv TELNET BINARY
option on output.
.It Ic crlf
If this is
.Dv TRUE ,
then carriage returns will be sent as
.Li <CR><LF> .
If this is
.Dv FALSE ,
then carriage returns will be send as
.Li <CR><NUL> .
The initial value for this toggle is
.Dv FALSE .
.It Ic crmod
Toggle carriage return mode.
When this mode is enabled, most carriage return characters received from
the remote host will be mapped into a carriage return followed by
a line feed.
This mode does not affect those characters typed by the user, only
those received from the remote host.
This mode is not very useful unless the remote host
only sends carriage return, but never line feed.
The initial value for this toggle is
.Dv FALSE .
.It Ic debug
Toggles socket level debugging (useful only to the
.Ic super user ) .
The initial value for this toggle is
.Dv FALSE .
.It Ic encdebug
Turns on debugging information for the encryption code.
Note that this flag only exists if encryption support is available.
.It Ic localchars
If this is
.Dv TRUE ,
then the
.Ic flush  ,
.Ic interrupt ,
.Ic quit  ,
.Ic erase ,
and
.Ic kill
characters (see
.Ic set
above) are recognized locally, and transformed into (hopefully) appropriate
.Tn TELNET
control sequences
(respectively
.Ic ao  ,
.Ic ip ,
.Ic brk  ,
.Ic ec ,
and
.Ic el  ;
see
.Ic send
above).
The initial value for this toggle is
.Dv TRUE
in \*(Lqold line by line\*(Rq mode,
and
.Dv FALSE
in \*(Lqcharacter at a time\*(Rq mode.
When the
.Dv LINEMODE
option is enabled, the value of
.Ic localchars
is ignored, and assumed to always be
.Dv TRUE .
If
.Dv LINEMODE
has ever been enabled, then
.Ic quit
is sent as
.Ic abort  ,
and
.Ic eof and
.B suspend
are sent as
.Ic eof and
.Ic susp ,
see
.Ic send
above).
.It Ic netdata
Toggles the display of all network data (in hexadecimal format).
The initial value for this toggle is
.Dv FALSE .
.It Ic options
Toggles the display of some internal
.Nm telnet
protocol processing (having to do with
.Tn telnet
options).
The initial value for this toggle is
.Dv FALSE .
.It Ic prettydump
When the
.Ic netdata
toggle is enabled, if
.Ic prettydump
is enabled the output from the
.Ic netdata
command will be formatted in a more user-readable format.
Spaces are put between each character in the output, and the
beginning of
.Tn telnet
escape sequences are preceded by a '*' to aid in locating them.
.It Ic skiprc
When the skiprc toggle is
.Dv TRUE ,
.Tn telnet
does not read the 
.Pa \&.telnetrc
file.  The initial value for this toggle is
.Dv FALSE.
.It Ic termdata
Toggles the display of all terminal data (in hexadecimal format).
The initial value for this toggle is
.Dv FALSE .
.It Ic verbose_encrypt
When the
.Ic verbose_encrypt
toggle is
.Dv TRUE ,
.Tn TELNET
prints out a message each time encryption is enabled or
disabled.  The initial value for this toggle is
.Dv FALSE.
This flag only exists if encryption support is available.
.It Ic \&?
Displays the legal
.Ic toggle
commands.
.El
.It Ic z
Suspend
.Nm telnet  .
This command only works when the user is using the
.Xr csh  1  .
.It Ic \&! Op Ar command 
Execute a single command in a subshell on the local
system.  If
.Ic command
is omitted, then an interactive subshell is invoked.
.It Ic \&? Op Ar command 
Get help.  With no arguments,
.Nm telnet
prints a help summary.
If a command is specified,
.Nm telnet
will print the help information for just that command.
.El
.Sh ENVIRONMENT
.Nm Telnet
uses at least the
.Ev HOME ,
.Ev SHELL ,
.Ev DISPLAY ,
and
.Ev TERM
environment variables.
Other environment variables may be propagated
to the other side via the
.Dv TELNET ENVIRON
option.
.Sh FILES
.Bl -tag -width ~/.telnetrc -compact
.It Pa ~/.telnetrc
user customized telnet startup values
.El
.Sh HISTORY
The
.Nm Telnet
command appeared in
.Bx 4.2 .
.Sh NOTES
.Pp
On some remote systems, echo has to be turned off manually when in
\*(Lqold line by line\*(Rq mode.
.Pp
In \*(Lqold line by line\*(Rq mode or 
.Dv LINEMODE
the terminal's
.Ic eof
character is only recognized (and sent to the remote system)
when it is the first character on a line.
.Sh BUGS
The source code is not comprehensible.