Provided by: sympathy_1.2.1+woking+cvs+git20171124_amd64 
NAME
sympathy - client/server terminal emulator with logging
SYNOPSIS
sympathy -t [ terminal_options ] [ display_options ]
sympathy -s [ terminal_options ] [ server_options ]
sympathy [ -c -s ] [ terminal_options ] [ server_options ] [ client_options ] [
display_options ]
sympathy -c [ client_options ] [ display_options ]
sympathy -r id [ client_options ] [ display_options ]
sympathy -C -d serialdev
sympathy -ls
sympathy -v
DESCRIPTION
Sympathy is a replacement for screen(1), minicom(1) and consolidate(1). It is a
VT52/VT100/ANSI terminal emulator with some special features. In normal use sympathy would
sit between a terminal device (a serial port or a pseudo-tty) and the user's usual
terminal emulator (eg xterm(1)). Sympathy renders data from the terminal device into an
internal frame buffer and then expresses changes in this frame buffer to the outer
terminal emulator using a small subset of ANSI escape codes. Sympathy always generates
valid escape codes to the outer terminal, and will reset the state of its internal
terminal emulator when it detects receive errors on the terminal device.
Sympathy, unlike screen(1), takes care to preserve the scroll-back features of the outer
terminal emulator: lines that scroll off the top of the internal frame buffer are scrolled
off the top of the outer terminal emulator. When sympathy is used in client/server mode,
some history is added to the outer terminal emulator when the client connects.
Sympathy also supports automatic baud-rate detection, and advanced logging features.
Sympathy logs whenever any of the modem control lines change state, receive errors, and
the contents of any line on the frame buffer as the cursor moves off it.
OPTIONS
major mode options:
-C clear lock files sympathy will remove inactive lockfiles for the specified serial
device, and then exit.
-c or -r id
act as client only: sympathy connects to a sympathy server process and injects the
history into the outer terminal emulator, and connects the user with the terminal
device. One server process can support multiple client processes. This mode can also
be used to obtain a dump of the current screen in HTML format (see the -H option),
inject key-presses (see -I) or allow control via a dumb terminal (see -N). The -r
option connects to a server process socket called id, or if id is an integer host-
name.id mimicking the behaviour of screen(1). Sympathy searches for the socket in
the following directories: ~/.sympathy, ~/sympathy, /etc/sympathy, /var/sympathy.
With the -c option the socket must be specified with the -k option.
[ -c -s ]
act as both client and server: sympathy forks. The child process becomes a server,
and the original process becomes a client which then connects to the server. This is
the default major mode if no other is specified. Since the default terminal device
is a pseudo-tty, running sympathy with no arguments will start a new shell in a
daemonised process and connect to it as a client from the original process, mimicking
the behaviour of screen(1)
-l or -ls
show active sockets: sympathy will show active sockets, ones to which a call to
connect(2) succeeds, in ~/.sympathy. If the socket name begins with the host-name of
the machine, and the call to connect(2) fails, then socket will be unlinked.
-s act as server only: sympathy opens the terminal device and renders into an internal
frame buffer, listens for clients on the socket and logs activity. By default the
server will fork into a daemon process but can be forced to remain in the foreground
with the -F option.
-t act as terminal emulator only: sympathy opens the terminal device and outputs into
the outer terminal emulator. When sympathy exits the device is closed and no process
remains. In this mode sympathy behaves like a traditional terminal emulator such as
cu(1) or minicom(1).
-v show current version: sympathy will print the the version number of the code it was
compiled from.
-h show help: sympathy will show brief usage instructions
terminal_options:
-d serialdev
connect to terminal device serialdev, eg /dev/ttyS0. By default sympathy doesn't
lock the terminal device, but checks periodically for lock files of other processes.
If sympathy detects another lock file it displays Locked in the status line and
refuses I/O on the device until the lock file is removed or becomes invalid. To lock
the device use the -K option. Sympathy will in addition check that the name of the
device does not occur in /proc/cmdline as an argument to the console kernel
parameter. The -d option is incompatible with the -p option.
-p connect to a pseudo-tty instead of a terminal device, and fork a login shell in it.
The -p option is incompatible with the -d option. This is the default terminal device
if none is specified. The first non-option command line arugment is considered to be
the a binary to run in the pseudo-tty, subsequent arguments are parsed to the binary.
The current value of PATH is searched for the binary if it does not start with '/'.
If no binary is specified then '/bin/sh' is called with argv[0] set to '-'.
-K lock the terminal device specified in the -d option. Sympathy generates lock files
in a staggering variety of formats and places. For locks based on the name of the
device sympathy generates lock files for all devices with the same major and minor in
/dev, /dev/usb and /dev/tts, it uses both normal and lower case and replaces
occurrences of `/' in the device name with both `.' and `_'. Sympathy also generates
locks based on the device major and minor numbers, and for all lock file names
generates them in any of the following directories that are writable: /var/lock/uucp,
/var/spool/lock, /var/spool/uucp, /etc/locks, /usr/spool/uucp, /var/spool/locks,
/usr/spool/lock, /usr/spool/locks, /usr/spool/uucp/LCK, /var/lock. Lock files are
assumed to be in HDB format.
-b baud-rate
set the baud-rate of the terminal device specified in the -d to baud-rate, if omitted
the current baud-rate of the serial port will be used.
-f turn on flow control on the terminal device. This option adds CRTSCTS to sympathy's
default c_cflags of CS8|CREAD|CLOCAL.
-L logfile
log activity to the file logfile. If logfile is `-' then log to stdout. Note that
logging to stdout only makes sense with the -F server_option. Sympathy will also
close and reopen its log file when it receives a SIGHUP, which with the -P allows the
use of logrotate(8).
-P pidfile
write the pid of the server/terminal process to pidfile, which is removed on clean
exit.
-R rotate log files. When the log-file specified with the -L option grows large sympathy
will rotate it and compress old log-files.
-w width[xheight]
set the initial size of the terminal emulator's frame buffer to be width columns by
height rows. If height is omitted it defaults to 24, the default width is 80. These
values may be overridden later by terminal escape sequences. If -p is also specified
the pseudo-tty will have its window size set to match.
display_options:
-u attempt to render Unicode characters in the internal frame buffer to the outer
terminal emulator by using ISO-2202 sequences. Sympathy currently only checks to see
if an appropriate character appears in the VT102 US character set, or in the VT102
`special characters and line drawing' character set. If the character appears in
neither of these then it will be rendered on the outer terminal emulator as a `?'.
-H render the current state of the internal frame buffer to stdout as HTML, then quit.
-N don't render the internal frame buffer using ANSI characters, but instead write
characters that would be written to the screen to stdout. Take characters from stdin
and send them to the device. This feature is useful when you wish to use sympathy in
conjunction with programs like expect(1).
client_options:
-k socket
set the name in the file-system of the socket to which sympathy should connect. This
option is mandatory unless the -s or -r options have also been given. If -s is given
then it will default to the socket which the forked server process opens. See the
discussion of the -r option above, for information on how sympathy chooses a socket
name if -r is specified.
-I string
Inject string to the device as if it had been typed at the keyboard. Each character
in the string is treated as a key-press. Sympathy recognizes various common escapes
for control characters. Other keys, for example the arrow keys, are mapped to
character codes between 128 and 255, see src/keys.h for details.
server_options:
-F tells the sympathy server process not to become a daemon but to remain the the
foreground. This option is incompatible with the -c -s major mode.
-k socket
set the name in the file-system of the socket on which sympathy should listen for
clients. If this option is omitted sympathy will create a socket in ~/.sympathy,
creating that directory if necessary, and named host-name.pid where pid is the
process id of the sympathy process that created the socket.
-n nlines
sets the number of lines of history that the server process stores to nlines. When a
client connects nlines of history are injected into the outer terminal emulator so
that they can be seen when scrolling back. By default the server stores 200 lines of
history.
-S tells the sympathy server process to log errors to syslog.
OPERATION
When sympathy is relaying data to the outer terminal emulator a reverse video status line
will be visible at the bottom of the screen. The status line shows pertinent information.
The first item on the line reminds you what the current escape character is, the second
indicates the terminal device to which sympathy is connected, and the third shows the
current baud-rate. Other messages are:
Flow indicates that that RTS/CTS flow control is in operation on the terminal device.
RTS indicates that the terminal device is asserting the RTS line which indicates that the
local system is ready to accept data from the remote system. If RTS/CTS flow control
is in operation then the operating system or hardware may de-assert RTS even if RTS
is shown. See the section on SERIAL PORT THEORY for more information.
CTS indicates that the terminal device has detected that the local system's CTS line is
being asserted, indicating that the remote system is ready to receive data from the
local system. See the section on SERIAL PORT THEORY for more information.
DTR indicates that the terminal device is asserting the DTR line indicating that the
local system would like the local DCE to establish a connection to the remote DCE.
See the section on SERIAL PORT THEORY for more information.
DSR indicates that the terminal device has detected that the local system's DSR line is
being asserted, indicating that the local DCE is ready. See the section on SERIAL
PORT THEORY for more information.
CD indicates that the terminal device has detected that the local system's CD line is
being asserted, indicating that the local DCE has a connection to the remote DCE.
See the section on SERIAL PORT THEORY for more information.
RI indicates that the terminal device has detected that the local system's RI line is
being asserted, indicating that the DCE has detected a ringing signal or incoming
connexion.
n clients
shows the number of connected client processes. In the -t major mode, this will
always be zero.
Locked
the terminal device was opened without the -K flag and another process is currently
using it. I/O to the device is currently suspended until the process dies or removes
its lock file.
n errs
indicates the number of frames received by the terminal device with errors
(indicating the wrong parity, baud-rate or framing). The count resets if no errors
are detected by the device for 10 seconds.
try higher
Sympathy thinks that you have set the wrong baud-rate and is unable to determine the
correct one as the current baud-rate is lower than the correct baud-rate. Use the
baud command to set a higher baud-rate (eg 115200) and sympathy will try again.
try rateb
Sympathy thinks that you have set the wrong baud-rate and thinks that the correct
baud-rate is rate. Use the baud command to change the current baud-rate.
COMMANDS
Commands are entered by sending the escape character, ascii(7) STX, from the outer
terminal emulator (usually by pressing CTRL-B), typing the command and pressing return.
Whilst the command is entered the status line changes to `:' and rudimentary line editing
is available. Whilst the command is entered the cursor does not move but remains where
the terminal emulator has placed it. Pressing the escape character whilst in command mode
will send the escape character to the terminal and cancel command mode. Valid commands
are:
ansi switch from VT102 behaviour to ANSI behaviour. The most noticeable difference is
the so-called `xn' glitch.
noansi switch from ANSI behaviour to VT102 behaviour.
baud nnnn
set the current baud-rate to nnnn
break send the break signal by asserting the TX line for longer than a frame period.
flow enable RTS/CTS flow control
noflow disable RTS/CTS flow control
hangup de-assert DTR for one second.
width nn
set the current width of the screen to nn, and reset the terminal emulator.
height nn
set the current height of the screen to nn, and reset the terminal emulator.
reset reset the terminal emulator
expand expand the size of the screen to fit the size of the current outer terminal
emulator window
quit exit this instance of sympathy (disconnect from the server if present)
CHARACTER ENCODINGS
For characters between 32 and 126 sympathy interprets them as would a VT102 terminal by
following the subset of ISO-2202 that the VT102 supports. Characters 128 thru 255 are
assumed to be in UTF-8(7), if however the UTF-8 is invalid they will instead be
interpreted as characters from ISO_8859-1(7). Character 155 (0x9b) when not part of a
valid UTF-8 sequence will be interpreted as the one byte CSI character.
For the outer terminal emulator sympathy by default issues the ESC % G sequence to select
UTF-8 mode and emits valid UTF-8. If the outer terminal does not, however, support UTF-8
use the -u switch to force sympathy to use the VT102 subset of ISO-2202.
LOG FILES
Log files are made exclusively in the UTF-8 encoding. Each line in the log file starts
with the date and time at which the entry was made - for example:
Feb 27 23:24:42.509440
Sympathy logs a line to the file whenever the cursor leaves the line. Additionally
sympathy
• logs certain other events to the file:
• serial port parameter changes: baud-rate and flow control.
• serial port control line state changes.
• serial port line discipline errors.
• serial port errors.
• suggested baud rates and bit frequency analyses.
• transmission of breaks.
• sending of the hangup signal (dropping the DTR line).
• unknown or un-handled messages sent on the socket.
• connexion and disconnexion of clients.
• reception of SIGHUP.
• invalid UTF-8 sequences.
• terminal size changes
• un-handled terminal command sequences
The log file is rotated when it gets too large if the -R option is specified, and the log
file is re-opened on receipt of a SIGHUP which together with the -P allows the use of of a
program such as logrotate(8)
AUTOMATIC BAUD RATE ALGORITHM
If sympathy detects a framing error on the serial port it displays the count of errors on
the status line, and logs the error.
<tty reports error: \377 \000 \000>
The count is reset to zero after ten seconds have elapsed during which no errors have
occurred. Sympathy looks at bit patterns of the characters received, and measures the
length (in units of the receiving UART's bit period) of any runs of '1's delimited by '0's
and vice-versa. It then calculates the statistics on the length of these runs, and logs
these.
<tty_bit_analyse: 0000000001 [0,0,0,0,0,0,110,0,0,80]>
For a typical stream of ASCII data, the most common run length will be the correct bit
period. Sympathy uses this together with the current bit period to calculate the most
probable correct baud-rate, which is displayed in the status line, and logged. If the
correct baudirate is higher than the current baud-rate then the most common bit frequency
will be '0' or '1' and the correct baud-rate cannot be determined. In this case sympathy
will display and log the message 'try higher'.
<tty_analyse: 80 errors, current rate 115200b, suggest 19200b>
The algorithm only works well if the data stream is normal. If the data stream is
generated by the reception, at the wrong baud-rate, of characters emitted by sympathy then
the algorithm will be biased towards suggesting that the baud-rate is too low. Noise on
the line will also result in sympathy concluding that the baud-rate is too low.
SIGNALS
Sympathy reacts to a set of signals. You can use the -P option to easily determine the PID
of the sympathy process to which you would like to send a signal.
SIGINT Sympathy will immediately try to restore the outer terminal emulator to its
original state and then exit.
SIGHUP Sympathy will close and reopen the log-file specified with the -L option, which
allows the use of programs like logrotate(8)
SIGWINCH
Sympathy will redraw the display in the outer terminal emulator so that it will
fit within the new display size.
SIGCHLD Sympathy will wait for children if some were born (for example from compressing
rotated logs)
ENVIRONMENT
sympathy uses the HOME environment variable to determine the default location for sockets.
sympathy sets the value of TERM in pseudo-ttys spawned using the -p argument to `xterm'.
Sympathy will use CSI ] 0 ; to set the window title to the name of the socket or device if
TERM starts with xterm or rxvt.
The PATH enviroment variable is searched for the binary to be run in the pseudo-tty.
EMULATION
Sympathy completely emulates a VT102 terminal (including the VT52 emulation). Sympathy
also emulates a few extra sequences: the xterm(1) ESC ] ... sequences, and the ANSI CSI @
and CSI b sequences. The numeric keypad follows exactly the sequences produced by an xterm
rather than the exact VT102/VT220 sequences. Sympathy also recognises the ESC % G and the
ESC % @ sequences to switch between ISO-2202 and UTF-8 but ignores them (see CHARACTER
ENCODING below)
SERIAL PORT THEORY
A serial connexion was originally envisaged to connect a DTE (Data Terminal Equipment) to
a DCE (Data Circuit-terminating Equipment). The DCE (some sort of modem) would assert the
DTE's (the computer or terminal) DSR line to indicate it was ready. The DTE would assert
DTR to indicate to the DCE that it should attempt a connexion to the remote DCE. Once a
connexion was established the DCE would assert the DTE's CD pin. Data could then flow
between the DTR and the remote DTE via the two DCEs. Flow control was provided via the RTS
and CTS lines. The DTE asserts RTS when it is capable of receiving new data, and pauses
its transmission of data when the CTS line is de-asserted. The local DCE asserts CTS when
the remote DCE detects RTS, and vice versa.
In modern usage the signals are slightly different, for a typical connexion using modems
DSR indicates that the modem is ready, a drop DTR is used to indicate to the modem that it
should break the connexion to the remote modem. CD indicates that the local modem is
connected to the remote modem, and CTS and RTS behave as before. Connexion is established
by in-band signalling before CD is asserted.
For a null modem cable local DSR and DTR are wired to remote CD, local CTS to remote RTS,
and local RTS to remote CTS. Thus asserting local DTR asserts local DSR and remote CD, and
asserting local RTS asserts remote CTS.
When RTS/CTS flow control is in operation and the receive buffer becomes full, the
operating system, or the hardware, de-asserts RTS, causing (via the DCEs or the null modem
cable) a de-assertion of remote CTS which in turn causes the remote DTE to cease
transmission.
EXAMPLES
using sympathy to mimic screen(1):
[foo@barhost ~]$ sympathy
Sympathy forks. The child becomes a daemon server and launches a new shell in a
pseudo-tty, the original process becomes a client and connects to the server and
shows the output. The user then uses the new shell and after some time either hangs
up on the client or issues CTRL-B quit, and the client detaches from the server.
Later the user wishes to retrieve her session and to determine which sympathy
sessions are active and issues:
[foo@barhost ~]$ sympathy -ls
/home/foo/.sympathy/barhost.8843 (Active)
[foo@barhost ~]$
The user then issues:
[foo@barhost ~]$ sympathy -r 8843
and is reconnected to her session.
using sympathy to mimic minicom(1):
[foo@barhost ~]$ sympathy -t -d /dev/modem -b 9600 -K
Sympathy opens the device /dev/modem and locks it, sets the baud-rate to 9600 baud
and disables flow control. A VT102 terminal emulator then displays the data from
the modem. The user quits the emulator by issuing CTRL-B quit, which unlocks the
modem and exits sympathy.
using sympathy to mimic consolidate(1):
[foo@barhost ~]$ sympathy -s -d /dev/ttyS13 -b 19200 -K -k /var/sympathy/13 -L
/var/sympathy/13.log -R
Sympathy becomes a daemon and detaches from the current tty. It then opens the
device /dev/ttyS13 and locks it, sets the baud-rate to 19200 baud and disables flow
control. Sympathy then listens for clients connecting on the socket
/var/sympathy/13, whilst logging completed lines and changes in status to the file
/var/sympathy/13.log, rotating the log file when it gets too large.
A user wishing to see the current status of /dev/ttyS13 issues:
[foo@barhost ~]$ sympathy -c -k /var/sympathy/13
or
[foo@barhost ~]$ sympathy -r 13
and the last 200 lines of history are injected into the history of her outer
terminal emulator and she is connected to /dev/ttyS13. The user disconnects from
the server by issuing CTRL-B quit.
using sympathy to mimic script(1):
[foo@barhost ~]$ sympathy -t -L typescript
Sympathy starts a shell in a ptty and logs completed lines to the file typescript.
When the shell exits sympathy will terminate, or the user can press CTRL-B which
will close the ptty and send a hangup to its controlling process.
SEE ALSO
screen(1) minicom(1) consolidate(1)
STANDARDS
ANSI X3.64, ISO-6429, ECMA-48, ISO-2202, ISO-8859, ISO-10646, Digital Equipment Corp.
VT102.
BUGS
• The command editor and parser should support better line editing.
• It should be possible to change the escape character.
• The HTML generated with the -H option is ugly.
• No useful error message is generated if opening the terminal device fails in the -c -s
major mode.
AUTHOR
James McKenzie, sympathy@madingley.org