| TELNET(1) | General Commands Manual | TELNET(1) |
telnet —
telnet |
[-468acdEFfKLNrx] [-e
escapechar] [-k
realm] [-l
user] [-n
tracefile] [-P
policy] [-S
tos] [-X
authtype] [host
[port]] |
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.
Options:
-4telnet to use IPv4 addresses only.-6telnet to use IPv6 addresses only.-8TELNET BINARY option on both input and
output.-E-F-F option allows the local credentials to be
forwarded to the remote system, including any credentials that have
already been forwarded into the local environment.-K-L-N-S
tos-X
atype-aUSER 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.-ctoggle skiprc command on this man
page.)-ddebug toggle to
TRUE.-e
escape chartelnet escape character to
escape char. If escape char is
omitted, then there will be no escape character.-f-f option allows the local credentials to be
forwarded to the remote system.-k
realm-k
option requests that telnet obtain tickets for the remote host in realm
realm instead of the remote host's realm.-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
tracefileset tracefile command below.-P
policy-r-e option.-xtelnet 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, then 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.
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).
auth
argument ...TELNET AUTHENTICATE option. Valid arguments for
the auth command are as follows:
disable
typeauth disable ?
command.enable
typeauth enable ?
command.statusclosedisplay
argument ...set and
toggle values (see below).encrypt
argument ...TELNET ENCRYPT option.
telnet is weak and insecure.Valid arguments for the encrypt command are:
disable
type [input|output]encrypt disable ?
command.enable
type [input|output]encrypt enable ?
command.inputencrypt start input
command.-inputencrypt stop input
command.outputencrypt start output
command.-outputencrypt stop output
command.start
[input|output]input and output, both
input and output are enabled. To obtain a list of available types, use
the encrypt enable ? command.statusstop
[input|output]type
typeencrypt start or encrypt
stop commands.environ
arguments ...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.logoutTELNET 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
typecharacterTELNET LINEMODE option, or, if the
remote side does not understand the LINEMODE
option, then enter “character at a time“ mode.lineTELNET 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 [-l
user] [-a]
[[-]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(3)). The
-l option may be used to specify the user name to
be passed to the remote system via the ENVIRON
option. If a port is specified telnet omits any
automatic initialisation 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 read.
Lines beginning with a # are comment lines. Blank lines are ignored.
Lines that begin without white space are the start of a machine entry.
The first thing on such a line is a string identifying the machine that
is being connected to. It may be the hostname or numeric address
specified as the argument host, the canonical name
of that string as determined by
getaddrinfo(3), or
the string “DEFAULT” indicating all hosts. The rest of the
line, and successive lines that begin with white space are assumed to be
telnet commands and are processed as if they had
been typed in manually to the telnet command
prompt.
quittelnet. An
end of file (in command mode) will also close a session and exit.send
argumentsabortTELNET ABORT (Abort processes)
sequence.aoTELNET AO (Abort Output) sequence,
which should cause the remote system to flush all output
from the remote system to the
user's terminal.aytTELNET AYT (Are You There) sequence,
to which the remote system may or may not choose to respond.brkTELNET BRK (Break) sequence, which
may have significance to the remote system.ecTELNET EC (Erase Character)
sequence, which should cause the remote system to erase the last
character entered.elTELNET EL (Erase Line) sequence,
which should cause the remote system to erase the line currently being
entered.eofTELNET EOF (End Of File)
sequence.eorTELNET EOR (End of Record)
sequence.escapetelnet escape character
(initially “^”).gaTELNET GA (Go Ahead) sequence, which
likely has no significance to the remote system.getstatusTELNET STATUS
command, getstatus will send the
subnegotiation to request that the server send its current option
status.ipTELNET IP (Interrupt Process)
sequence, which should cause the remote system to abort the currently
running process.nopTELNET NOP (No OPeration)
sequence.suspTELNET SUSP (SUSPend process)
sequence.synchTELNET 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
cmddont
cmdwill
cmdwont
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.?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.
aytLINEMODE
is enabled, and the status character is typed, a
TELNET AYT sequence (see send
ayt above) is sent to the remote host. The initial value for
the "Are You There" character is the terminal's status
character.echoeoftelnet 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.erasetelnet 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.escapetelnet escape character (initially
“^[”) which causes entry into
telnet command mode (when connected to a
remote system).flushoutputtelnet 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.forw1forw2LINEMODE, 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.interrupttelnet 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.killtelnet 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.lnexttelnet 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.quittelnet 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.reprinttelnet 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.rlogintelnet command. The initial
state is to disable the rlogin escape character.startTELNET 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.stopTELNET 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.susptelnet 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.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).worderasetelnet 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.
checkexporttelnet was started.import?slc
command.statustelnet. This includes
the peer one is connected to, as well as the current mode.toggle
arguments ...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:
authdebugautoflushautoflush 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)).autodecryptTELNET 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.
telnet is weak and insecure.autologinTELNET
AUTHENTICATION option TELNET attempts to use it to perform
automatic authentication. If the
AUTHENTICATION option is not supported, the
user's login name are propagated through the TELNET
ENVIRON option. This command is the same as specifying the
-a option on the open
command.autosynchautosynch and
localchars are both
TRUE, then when either the
intr or quit
characters 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.binaryTELNET BINARY option on
both input and output.inbinaryTELNET BINARY option on
input.outbinaryTELNET BINARY option on
output.crlfTRUE, then carriage returns will be
sent as <CR><LF>. If this is
FALSE, then carriage returns will be send as
<CR><NUL>. The initial value for
this toggle is FALSE.crmodFALSE.debugsuper user). The initial value for this toggle
is FALSE.encdebuglocalcharsTRUE, 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).netdataFALSE.optionstelnet
protocol processing (having to do with TELNET options). The initial
value for this toggle is FALSE.prettydumpnetdata 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.skiprcTRUE, TELNET skips
the reading of the .telnetrc file in the users
home directory when connections are opened. The initial value for this
toggle is FALSE.termdataFALSE.verbose_encryptverbose_encrypt toggle is
TRUE, telnet prints
out a message each time encryption is enabled or disabled. The initial
value for this toggle is FALSE. Note: Because
of export controls, data encryption is not supported outside of the
United States and Canada.?toggle commands.ztelnet. This command only works when the
user is using the csh(1).!
[command]?
[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,
SHELL, DISPLAY, and
TERM environment variables. Other environment
variables may be propagated to the other side via the TELNET
ENVIRON option.
telnet command appeared in
4.2BSD. IPsec support was added by WIDE/KAME project,
in 1999.
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.
| April 16, 2022 | NetBSD 10.1 |