TELNET(1) | General Commands Manual | TELNET(1) |
telnet
— user
interface to the TELNET protocol
telnet |
[-4678acDEKLr ]
[-b hostalias]
[-e escapechar]
[-l user]
[-n tracefile]
[-V rtable]
[host [port]] |
The telnet
command is used to communicate
with another host using the TELNET protocol. If
telnet
is invoked without the
host argument, it enters command mode, indicated by
its prompt (telnet>
). In this mode, it accepts
and executes the commands listed below. If it is invoked with arguments, it
performs an open
command with those arguments.
The options are as follows:
-4
telnet
to use IPv4 addresses only.-6
telnet
to use IPv6 addresses only.-7
TELNET BINARY
option on both input and
output.-8
TELNET BINARY
option on both input and output.
This is the default.-a
USER
variable of the
ENVIRON
option if supported by the remote system.
The name used is that of the current user as returned by
getlogin(2) if it agrees
with the current user ID, otherwise it is the name associated with the
user ID.-b
hostaliasalias
specifier) or to the address of another
interface than the one naturally chosen by
connect(2). This can be
useful when connecting to services which use IP addresses for
authentication and reconfiguration of the server is undesirable (or
impossible).-c
toggle skiprc
command on this man
page.)-D
DISPLAY
variable when it
starts with ‘:’ or ‘unix:’. By default, these
are replaced with the local hostname and a colon.-E
-e
escapechartelnet
escape character to
escapechar. If escapechar is
omitted, then there will be no escape character.-K
-L
TELNET BINARY
option on output.-l
userENVIRON
option, then user
will be sent to the remote system as the value for the variable USER. This
option implies the -a
option. This option may also
be used with the open
command.-n
tracefilenetdata
or option
tracing
being TRUE
, will be written. If it is set to
“-
”, then tracing information will
be written to standard output (the default).-r
rlogin
. In
this mode, the escape character is set to the tilde (~) character, unless
modified by the -e
option.-V
rtabletelnet
port is used.When in rlogin mode, a line of the form ~. disconnects from the remote host; ~ is the telnet escape character. Similarly, the line ~^Z suspends the telnet session. The line ~^] escapes to the normal telnet escape prompt.
Once a connection has been opened, telnet
will attempt to enable the TELNET LINEMODE
option.
If this fails, telnet
will revert to one of two
input modes: either “character at a time” or “old line
by line” depending on what the remote system supports.
When LINEMODE
is enabled, character
processing is done on the local system, under the control of the remote
system. When input editing or character echoing is to be disabled, the
remote system will relay that information. The remote system will also relay
changes to any special characters that happen on the remote system, so that
they can take effect on the local system.
In “character at a time” mode, most text typed is immediately sent to the remote host for processing.
In “old line by line” mode, all text is echoed locally, and (normally) only completed lines are sent to the remote host. The local echo character (initially ‘^E’) may be used to turn off and on the local echo (this would mostly be used to enter passwords without the password being echoed).
If the LINEMODE
option is enabled, or if
the localchars
toggle is
TRUE
(the default for “old line by
line”; see below), the user's quit
,
intr
, and flush
characters
are trapped locally, and sent as TELNET protocol sequences to the remote
side. If LINEMODE
has ever been enabled, then the
user's susp
and eof
are also
sent as TELNET protocol sequences, and quit
is sent
as a TELNET ABORT
instead of
BREAK
. There are options (see
toggle
autoflush
and
toggle
autosynch
below)
which cause this action to flush subsequent output to the terminal (until
the remote host acknowledges the TELNET sequence) and flush previous
terminal input (in the case of quit
and
intr
).
While connected to a remote host, telnet
command mode may be entered by typing the telnet
escape character (initially ‘^]’). When in command mode, the
normal terminal editing conventions are available. Note that the escape
character will return to the command mode of the initial invocation of
telnet
that has the controlling terminal. Use the
send escape
command to switch to command mode in
subsequent telnet
processes on remote hosts.
The following telnet
commands are
available. Only enough of each command to uniquely identify it need be typed
(this is also true for arguments to the mode
,
set
, toggle
,
unset
, slc
,
environ
, and display
commands).
close
display
argument ...set
and
toggle
values (see below).environ
argument ...environ
command is used to manipulate the
variables that may be sent through the TELNET
ENVIRON
option. The initial set of variables is taken from the
users environment, with only the DISPLAY
and
PRINTER
variables being exported by default. The
USER
variable is also exported if the
-a
or -l
options are used.
Valid arguments for the environ
command are:
define
variable valueundefine
variableexport
variableunexport
variablelist
*
will be sent automatically, other variables
will only be sent if explicitly requested.?
environ
command.logout
TELNET LOGOUT
option to the remote side.
This command is similar to a close
command;
however, if the remote side does not support the
LOGOUT
option, nothing happens. If, however, the
remote side does support the LOGOUT
option, this
command should cause the remote side to close the TELNET connection. If
the remote side also supports the concept of suspending a user's session
for later reattachment, the logout argument indicates that you should
terminate the session immediately.mode
typecharacter
TELNET LINEMODE
option or, if the
remote side does not understand the LINEMODE
option, then enter “character at a time” mode.line
TELNET LINEMODE
option or, if the
remote side does not understand the LINEMODE
option, then attempt to enter “old line by line”
mode.isig
(-isig
)TRAPSIG
mode
of the LINEMODE
option. This requires that the
LINEMODE
option be enabled.edit
(-edit
)EDIT
mode of
the LINEMODE
option. This requires that the
LINEMODE
option be enabled.softtabs
(-softtabs
)SOFT_TAB
mode
of the LINEMODE
option. This requires that the
LINEMODE
option be enabled.litecho
(-litecho
)LIT_ECHO
mode
of the LINEMODE
option. This requires that the
LINEMODE
option be enabled.?
mode
command.open
host [-a
]
[-b
-hostalias
]
[-l
user]
[[-
] port]telnet
will attempt to contact a TELNET server at
the default port. The host specification may be either a host name (see
hosts(5)) or an Internet
address specified in the “dot notation” (see
inet_ntop(3)). The
-a
, -b
, and
-l
options are equivalent to the identical command
line options, but only apply to the new telnet connection being opened.
When connecting to a non-standard port, telnet
omits any automatic initiation of TELNET options. When the port number is
preceded by a minus sign, the initial option negotiation is done. After
establishing a connection, the file .telnetrc in
the user's home directory is opened. Lines beginning with a
‘#’ are comment lines. Blank lines are ignored. Lines that
begin without whitespace are the start of a machine entry. The first thing
on the line is the name of the machine that is being connected to. The
rest of the line, and successive lines that begin with whitespace are
assumed to be telnet
commands and are processed as
if they had been typed in manually to the telnet
command prompt.quit
telnet
. An
end-of-file (in command mode) will also close a session and exit.send
argument ...abort
TELNET ABORT
(Abort processes)
sequence.ao
TELNET AO
(Abort Output) sequence,
which should cause the remote system to flush all output
from
the remote system
to the
user's terminal.ayt
TELNET AYT
(Are You There) sequence,
to which the remote system may or may not choose to respond.brk
TELNET BRK
(Break) sequence, which
may have significance to the remote system.ec
TELNET EC
(Erase Character)
sequence, which should cause the remote system to erase the last
character entered.el
TELNET EL
(Erase Line) sequence,
which should cause the remote system to erase the line currently being
entered.eof
TELNET EOF
(End Of File)
sequence.eor
TELNET EOR
(End of Record)
sequence.escape
telnet
escape character
(initially ‘^]’).ga
TELNET GA
(Go Ahead) sequence, which
likely has no significance to the remote system.getstatus
TELNET STATUS
command, getstatus
will send the
subnegotiation to request that the server send its current option
status.ip
TELNET IP
(Interrupt Process)
sequence, which should cause the remote system to abort the currently
running process.nop
TELNET NOP
(No OPeration)
sequence.susp
TELNET SUSP
(SUSPend process)
sequence.synch
TELNET SYNCH
sequence. This sequence
causes the remote system to discard all previously typed (but not yet
read) input. This sequence is sent as TCP urgent data (and may not
work if the remote system is a 4.2BSD system
-- if it doesn't work, a lower case ‘r’ may be echoed on
the terminal).do
cmdTELNET DO
cmd
sequence. cmd can be either a decimal number
between 0 and 255, or a symbolic name for a specific TELNET command.
cmd can also be either
help
or ?
to print out
help information, including a list of known symbolic names.dont
cmdTELNET DONT
cmd sequence. cmd can be
either a decimal number between 0 and 255, or a symbolic name for a
specific TELNET command. cmd can also be either
help
or ?
to print out
help information, including a list of known symbolic names.will
cmdTELNET WILL
cmd sequence. cmd can be
either a decimal number between 0 and 255, or a symbolic name for a
specific TELNET command. cmd can also be either
help
or ?
to print out
help information, including a list of known symbolic names.wont
cmdTELNET WONT
cmd sequence. cmd can be
either a decimal number between 0 and 255, or a symbolic name for a
specific TELNET command. cmd can also be either
help
or ?
to print out
help information, including a list of known symbolic names.?
send
command.set
argument valueunset
argument valueset
command will set any one of a number of
telnet
variables to a specific value or to
TRUE
. The special value
off
turns off the function associated with the
variable; this is equivalent to using the unset
command. The unset
command will disable or set to
FALSE
any of the specified functions. The values
of variables may be interrogated with the display
command. The variables which may be set or unset, but not toggled, are
listed here. In addition, any of the variables for the
toggle
command may be explicitly set or unset
using the set
and unset
commands.
ayt
localchars
mode, or
LINEMODE
is enabled, and the status character
is typed, a TELNET AYT
sequence (see
send ayt
preceding) is sent to the remote
host. The initial value for the "Are You There" character is
the terminal's status character.echo
eof
telnet
is operating in
LINEMODE
or “old line by line”
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 eof
character.erase
telnet
is in
localchars
mode (see
toggle
localchars
below), and if telnet
is operating in
“character at a time” mode, then when this character is
typed, a TELNET EC
sequence (see
send
ec
above) is sent
to the remote system. The initial value for the
erase
character is taken to be the terminal's
erase
character.escape
telnet
escape character (initially
‘^[’) which causes entry into
telnet
command mode (when connected to a
remote system).flushoutput
telnet
is in
localchars
mode (see
toggle
localchars
below) and the flushoutput
character is typed,
a TELNET AO
sequence (see
send
ao
above) is sent
to the remote host. The initial value for the
flush
character is taken to be the terminal's
flush
character.forw1
forw2
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.interrupt
telnet
is in
localchars
mode (see
toggle
localchars
below) and the interrupt
character is typed, a
TELNET IP
sequence (see
send
ip
above) is sent
to the remote host. The initial value for the
interrupt
character is taken to be the
terminal's intr
character.kill
telnet
is in
localchars
mode (see
toggle
localchars
below), and if telnet
is operating in
“character at a time” mode, then when this character is
typed, a TELNET EL
sequence (see
send
el
above) is sent
to the remote system. The initial value for the
kill
character is taken to be the terminal's
kill
character.lnext
telnet
is operating in
LINEMODE
or “old line by line”
mode, then this character is taken to be the terminal's
lnext
character. The initial value for the
lnext
character is taken to be the terminal's
lnext
character.quit
telnet
is in
localchars
mode (see
toggle
localchars
below) and the quit
character is typed, a
TELNET BRK
sequence (see
send
brk
above) is
sent to the remote host. The initial value for the
quit
character is taken to be the terminal's
quit
character.reprint
telnet
is operating in
LINEMODE
or “old line by line”
mode, then this character is taken to be the terminal's
reprint
character. The initial value for the
reprint
character is taken to be the
terminal's reprint
character.rlogin
telnet
command. The initial
state is to disable the rlogin
escape
character.start
TELNET TOGGLE-FLOW-CONTROL
option has
been enabled, then this character is taken to be the terminal's
start
character. The initial value for the
start
character is taken to be the terminal's
start
character.stop
TELNET TOGGLE-FLOW-CONTROL
option has
been enabled, then this character is taken to be the terminal's
stop
character. The initial value for the
stop
character is taken to be the terminal's
stop
character.susp
telnet
is in
localchars
mode, or
LINEMODE
is enabled, and the
suspend
character is typed, a
TELNET SUSP
sequence (see
send
susp
above) is
sent to the remote host. The initial value for the
suspend
character is taken to be the
terminal's suspend
character.worderase
telnet
is operating in
LINEMODE
or “old line by line”
mode, then this character is taken to be the terminal's
worderase
character. The initial value for the
worderase
character is taken to be the
terminal's worderase
character.?
set
(unset
) commands.slc
stateslc
command (Set Local Characters) is used to
set or change the state of the special characters when the
TELNET LINEMODE
option has been enabled. Special
characters are characters that get mapped to TELNET commands sequences
(like ip
or quit
) or line
editing characters (like erase
and
kill
). By default, the local special characters
are exported.
check
export
telnet
was started.import
?
slc
command.status
telnet
. This includes
the peer one is connected to, as well as the current mode.toggle
argument ...TRUE
and
FALSE
) various flags that control how
telnet
responds to events. These flags may be set
explicitly to TRUE
or
FALSE
using the set
and
unset
commands listed above. More than one
argument may be specified. The state of these flags may be interrogated
with the display
command. Valid arguments are:
autoflush
autoflush
and
localchars
are both
TRUE
, then when the ao
or quit
characters are recognized (and
transformed into TELNET sequences; see set
above for details), telnet
refuses to display
any data on the user's terminal until the remote system acknowledges
(via a TELNET TIMING MARK
option) that it has
processed those TELNET sequences. The initial value for this toggle is
TRUE
if the terminal user had not done an
"stty noflsh", otherwise FALSE
(see
stty(1)).autologin
TELNET ENVIRON
option. This command is the
same as specifying a option on the
open
command.autosynch
autosynch
and
localchars
are both
TRUE
, then when either the
intr
or quit
character
is typed (see set
above for descriptions of
the intr
and quit
characters), the resulting TELNET sequence sent is followed by the
TELNET SYNCH
sequence. This procedure
should
cause the remote system to begin throwing away all previously typed
input until both of the TELNET sequences have been read and acted
upon. The initial value of this toggle is
FALSE
.binary
TELNET BINARY
option on
both input and output.inbinary
TELNET BINARY
option on
input.outbinary
TELNET BINARY
option on
output.crlf
TRUE
, then carriage returns will be
sent as <CR><LF>
. If this is
FALSE
, then carriage returns will be sent as
<CR><NUL>
. The initial value for
this toggle is FALSE
.crmod
FALSE
.localchars
TRUE
, then the
flush
, interrupt
,
quit
, erase
, and
kill
characters (see
set
above) are recognized locally, and
transformed into (hopefully) appropriate TELNET control sequences
(respectively ao
, ip
,
brk
, ec
, and
el
; see send
above).
The initial value for this toggle is TRUE
in
“old line by line” mode, and
FALSE
in “character at a time”
mode. When the LINEMODE
option is enabled, the
value of localchars
is ignored, and assumed to
always be TRUE
. If
LINEMODE
has ever been enabled, then
quit
is sent as abort
,
and eof
and suspend
are sent as eof
and
susp
(see send
above).netdata
FALSE
.options
telnet
protocol processing (having to do with TELNET options). The initial
value for this toggle is FALSE
.prettydump
netdata
toggle is enabled, if
prettydump
is enabled the output from the
netdata
command will be formatted in a more
user readable format. Spaces are put between each character in the
output, and the beginning of any TELNET escape sequence is preceded by
a '*' to aid in locating them.skiprc
TRUE
, TELNET skips
the reading of the .telnetrc file in the
user's home directory when connections are opened. The initial value
for this toggle is FALSE
.termdata
FALSE
.?
toggle
commands.z
telnet
. This command only works when the
user is using a shell with job control enabled.?
[command]telnet
prints a help
summary. If a command is specified, telnet
will
print the help information for just that command.telnet
uses at least the
HOME
, DISPLAY
, and
TERM
environment variables. Other environment
variables may be propagated to the other side via the
TELNET ENVIRON
option.
The telnet
command appeared in
4.2BSD.
On some remote systems, echo has to be turned off manually when in “old line by line” mode.
In “old line by line” mode or
LINEMODE
the terminal's eof
character is only recognized (and sent to the remote system) when it is the
first character on a line.
November 13, 2015 | OpenBSD-5.9 |