irix - telnet (1)
NAME
telnet - user interface to the TELNET protocol
SYNOPSIS
telnet [-d] [-n tracefile] [-l user | -a] [-e escape-char] [host [port]]
DESCRIPTION
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 (see below) with those arguments.
Options:
-d Sets the initial value of the debug toggle to TRUE.
-n tracefile
Opens tracefile for recording trace information. See the set
tracefile command below.
-l user When connecting to the remote system, if the remote system
understands the ENVIRON option, user is sent to the remote
system as the value for the variable USER. This option can
also be used with the open command.
-a Auto-login. Same as specifying -l with your user name. This
option can also be used with the open command.
-e escape-char
Sets the initial telnet escape character to escape-char. If
escape-char is the null character (specified by "" or ''),
there is no escape character.
host Indicates the official name, an alias, or the Internet address
of a remote host.
port Indicates a port number (address of an application). If a
number is not specified, the default telnet port is used.
Once a connection has been opened, telnet attempts to enable the TELNET
LINEMODE option. If this fails, telnet reverts 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 relays that
information. The remote system relays 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) can 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, 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) that 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 can 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 needs to be typed (this is also true for
arguments to the mode, set, toggle, unset, slc, environ, and display
commands).
close Close a TELNET session and return to command mode.
display [ argument... ]
Display all, or some, of the set and toggle values (see below).
mode type type is one of several options, depending on the state of the
TELNET session. The remote host is asked for permission to go
into the requested mode. If the remote host is capable of
entering that mode, the requested mode is entered.
character Disable the TELNET LINEMODE option, or, if the remote
side does not understand the LINEMODE option, enter
"character at a time" mode.
line Enable the TELNET LINEMODE option, or, if the remote
side does not understand the LINEMODE option, attempt
to enter "old line by line" mode.
isig (-isig)
Attempt to enable (disable) the TRAPSIG mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
edit (-edit)
Attempt to enable (disable) the EDIT mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
softtabs (-softtabs)
Attempt to enable (disable) the SOFT_TAB mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
litecho (-litecho)
Attempt to enable (disable) the LIT_ECHO mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
? Print out help information for the mode command.
open host [ [-l user | -a] [-]port ]
Open a connection to the named host. If no port number is
specified, telnet attempts to contact a TELNET server at the
default port. The host specification can be either a hostname
(see hosts(4)) or an Internet address specified in the "dot
notation" (see inet(3N)). The -l option can be used to specify
the user name to be passed to the remote system via the ENVIRON
option. The -a option sends your user name to the remote
system via the ENVIRON option. 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 .telnetrc file 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 Close any open TELNET session and exit telnet. An end of file
(in command mode) also closes a session and exits.
send arguments
Send one or more special character sequences to the remote
host. The following are the arguments that can be specified
(more than one argument can be specified at a time):
abort Send the TELNET ABORT (ABORT processes) sequence.
ao Send the 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 Send the TELNET AYT (Are You There) sequence, to
which the remote system may or may not choose to
respond.
brk Send the TELNET BRK (Break) sequence, which may have
significance to the remote system.
ec Send the TELNET EC (Erase Character) sequence, which
should cause the remote system to erase the last
character entered.
el Send the TELNET EL (Erase Line) sequence, which
should cause the remote system to erase the line
currently being entered.
eof Send the TELNET EOF (End Of File) sequence.
eor Send the TELNET EOR (End of Record) sequence.
escape Send the current telnet escape character (initially
^]).
ga Send the TELNET GA (Go Ahead) sequence, which likely
has no significance to the remote system.
getstatus If the remote side supports the TELNET STATUS
command, getstatus sends the subnegotiation to
request that the server send its current option
status.
ip Send the TELNET IP (Interrupt Process) sequence,
which should cause the remote system to abort the
currently running process.
nop Send the TELNET NOP (No OPeration) sequence.
susp Send the TELNET SUSP (SUSPend process) sequence.
synch Send the 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 4.2 BSD system -- if it doesn't work, a
lower case r may be echoed on the terminal).
? Print out help information for the send command.
set argument value
unset arguments...
The set command sets any one of a number of telnet variables to
the function associated with the variable, this is equivalent
to using the unset command. The unset command disables or sets
to FALSE any of the specified functions. The values of
variables can be interrogated with the display command. The
variables that can be set or unset, but not toggled, are listed
here. In addition, any of the variables for the toggle command
can be explicitly set or unset using the set and unset
commands.
echo The value (initially ^E) which, when in "line by
line" mode, toggles between doing local echoing of
entered characters (for normal processing) and
suppressing echoing of entered characters (for
entering, say, a password).
eof If telnet is operating in LINEMODE or "old line by
line" mode, entering this character as the first
character on a line causes 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 If telnet is in localchars mode (see toggle
localchars below), and if telnet is operating in
"character at a time" mode, 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 The telnet escape character (initially ^[), which
causes entry into telnet command mode (when connected
to a remote system).
flushoutput
If 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.
interrupt If 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 If telnet is in localchars mode (see toggle
localchars below), and if telnet is operating in
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 If telnet is operating in LINEMODE or "old line by
line" mode, 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 If 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 If telnet is operating in LINEMODE or "old line by
line" mode, 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.
start If the TELNET TOGGLE-FLOW-CONTROL option has been
enabled, this character is taken to be the terminal's
start character. The initial value for the kill
character is taken to be the terminal's start
character.
stop If the TELNET TOGGLE-FLOW-CONTROL option has been
enabled, this character is taken to be the terminal's
stop character. The initial value for the kill
character is taken to be the terminal's stop
character.
susp If 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.
tracefile The file to which the output, caused by netdata or
option tracing being TRUE, is written. If it is set
to -, tracing information is written to standard
output (the default).
worderase If telnet is operating in LINEMODE or "old line by
line" mode, this character is taken to be the
terminal's worderase character. The initial value
terminal's worderase character.
slc state The slc 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.
export Switch to the local defaults for the
special characters. The local default
characters are those of the local terminal
at the time when telnet was started.
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 TELNET connection was
established.
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 switches to the remote value.
? Print out help information for the slc
command.
environ arguments...
The environ command is used to manipulate the
variables that can be sent through the ENVIRON
option. The initial set of variables is taken from
the user's environment with only the DISPLAY and
PRINTER variables being exported by default.
Valid arguments for the environ command are:
define variable value
Define the variable variable to have a
value of value. Any variables defined by
this command are automatically exported.
The value can be enclosed in single or
double quotes so that tabs and spaces can
be included.
undefine variable
Remove variable from the list of
environment variables.
export variable
Mark the variable variable to be exported
to the remote side.
unexport variable
Mark the variable variable to not be
exported unless explicitly asked for by the
remote side.
send variable
Send the variable variable to the remote
side.
list List the current set of environment
variables. Those marked with a * are sent
automatically, other variables are sent
only if explicitly requested.
? Print out help information for the environ
command.
? Display the legal set (unset) commands.
toggle arguments...
Toggle (between TRUE and FALSE) various flags that control how
telnet responds to events. These flags can be set explicitly
to TRUE or FALSE using the set and unset commands listed above.
More than one argument can be specified. The state of these
flags can be interrogated with the display command. Valid
arguments are:
autoflush If autoflush and localchars are both TRUE, when the
ao, intr, 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)).
autosynch If autosynch and localchars are both TRUE, 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.
binary Enable or disable the TELNET BINARY option on both
input and output.
inbinary Enable or disable the TELNET BINARY option on input.
outbinary Enable or disable the TELNET BINARY option on output.
crlf If this is TRUE, carriage returns are sent as
<CR><LF>. If this is FALSE, carriage returns are
sent as <CR><NUL>. The initial value for this toggle
is FALSE.
crmod Toggle carriage return mode. When this mode is
enabled, most carriage return characters received
from the remote host are mapped into a carriage
return followed by a linefeed. 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 linefeed. The initial value for
this toggle is FALSE.
debug Toggle socket level debugging (useful only to the
superuser). The initial value for this toggle is
FALSE.
localchars
If this is TRUE, 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, quit is sent as
abort, and eofand suspend are sent as eofand susp,
see send above).
netdata Toggle the display of all network data (in
hexadecimal format). The initial value for this
toggle is FALSE.
options Toggle the display of some internal telnet protocol
processing (having to do with TELNET options). The
initial value for this toggle is FALSE.
prettydump
When the netdata toggle is enabled, if prettydump is
enabled, the output from the netdata command is
put between each character in the output, and the
beginning of any TELNET escape sequence is preceded
by a * to aid in locating them.
? Display the legal toggle commands.
z Suspend telnet. This command only works when the user is using
the csh(1).
! [ command ]
Execute a single command in a subshell on the local system. If
command is omitted, an interactive subshell is invoked.
status Show the current status of telnet. This includes the peer one
is connected to, as well as the current mode.
? [ command ]
Get help. With no arguments, telnet prints a help summary. If
a command is specified, telnet prints the help information for
just that command.
ENVIRONMENT
telnet uses at least the HOME, SHELL, USER, DISPLAY, and TERM environment
variables. Other environment variables can be propagated to the other
side via the TELNET ENVIRON option.
FILES
~/.telnetrc user customized telnet startup values
NOTES
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.