Introduction
FLTerm(Fast Light Terminal, formally “tinyTerm2”) is a simple small scriptable terminal emulator, with unique features like command autocompletion, scp integration, batch automation, and scripting. It is a rewrite of tinyTerm using C++, FLTK, and libssh2. now cross platform with tabs support, and it is still very small, win64 executable is 825KB at current release, MacOS install package just below 1MB
| Stable release: | 2.1.0 | License: | GPL 3.0 |
|---|---|---|---|
| PC install: | Microsoft Store | 32bit EXE | 64bit EXE |
| Mac install: | Apple store | FLTerm.pkg |
Documentation
Making connections
A connection dialog will popup at the start of FLTerm, simply choose the protocol, type in port and ip address/hostname then press enter to make a connection. Each time a connection is make using dialog, an entry will be added to the Term menu, simply select the menu entry to make the same connection again. Six types of connections are supported: shell, serial, telnet, ssh, sftp and netconf, except that sandboxed Apple store app will block shell execution.
Once a connection is made, any key press will be transmitted to remote host, with response from host displayed in the terminal, most vt100/xterm escape sequences are supported, enough to work normally for top, vi, vttest etc.
Press left mouse button and drag to select text, double click to select the whole word under mouse pointer, selected text will be copied to clipboard when mouse is moved out of the terminal window. When text is selected, right click will paste selected text into the same terminal, when no text is selected, right click will paste from clipboard.
Scroll back buffer holds 64K lines of text, scrollbar is hidden by default, which will appear when scrolled back, use page up/page down key or mouse wheel to scroll. The buffer can be saved to a text file at any time, or turn logging function to write all terminal output to a text file.
Command history and autocompletion
Local Edit Mode was a feature on physical terminals used to save time on slow connections. On FLTerm local edit mode is used to implement command history and command auto-completion, which is useful to help users remember long commands and save time on typing.
When local edit mode is enabled, key presses are not sent to remote host until “Enter”, “Tab” or “?” key is pressed, and the input is auto completed using command history, user can also press “up” or “down” key to bring up the command history list, then select command from the list to send to host. Every command typed in local edit mode is added to command history, which saved to tinyTerm.hist at exit, then loaded into memory at the next start of tinyTerm.
Additionally when disconnected with local edit mode enabled, user is presented with a “FLTerm >” prompt, simply type commands like “telnet 192.168.1.1” or “ssh admin@172.16.1.1” to make conection
Transfer files to remote host
Drag and drop files to the terminal window will get the files transfered to remote host, placed in the current working directory
on ssh connection files are copied via scp on sftp connection files are copied via sftp put on netconf connection the files content will be sent as xml on serial connection first file will be sent using xmodem protocol
only send function of the original xmodem protocol is supported, CRC optional. This is added to support bootstraping of MCUs on embeded system like Ardiuno
Task Automation with batch commands
To automate tasks, simply drag and drop a list of commands to the terminal, tinyTerm send one command at a time, wait for prompt string before sending the next command, to avoid overflowing the receive buffer of the remote host or network device.
Most command line interface system uses a prompt string to tell user it’s ready for the next command, for example “> “ or “$ “ used by Cisco routers. tinyTerm will auto detect the prompt string used by remote host when a batch is dropped. Additionally, prompt string can be set in the script using command “!Prompt {str}”, refer to appendix A for details and other special commands supported for scripting.
A few local command like “Wait”, “Clear”, “Log” etc to enance the automation, the example below automate the task of connecting to a host, list some files, run top and log everthing to a file
!Prompt $%20 !Log top.log !ssh pi@192.168.12.8 ls -l !Wait 3 top -b -n 3 !Log exit
Scripting interface
More complex automation is facilited through the xmlhttp interface, a built in HTTPd listens at 127.0.0.1:8080, and will accept GET request from local machine, which means any program running on the same machine, be it a browser or a javascript or any program that supports xmlhttp interface, can connect to tinyTerm and request either a file or the result of a command,
for example:
http://127.0.0.1:8080/FLTerm.html return FLTerm.html from current working folder
http://127.0.0.1:8080/?ls -al return the result of "ls -al" from remote host
http://127.0.0.1:8080/?!Selection return current selected text from scroll back buffer
Notice the “!” just before “Selection” in the last example, when a command is started with “!”, it’s being executed by tinyTerm instead of sent to remote host, There are about 30 tinyTerm commands supported for the purpose of making connections, setting options, sending commands, scp files, turning up ssh2 tunnels, see appendix for the list.
The snippet below shows how to call the xmlhttp interfaces from javascript. An example in github/FLTerm/scripts, xmlhttp_get.html, demostrates a simple webpage, which takes a command from input field, send it through FLTerm, and present the result in browser
var xhr = new XMLHttpRequest();
function xmlhttp(cmd) {
xhr.open('GET', "/?"+cmd, false);
xhr.send(null);
return xhr.responseText;
}
The following commands can be used programatically for scripting
!/bin/bash start local shell, on Windows try "ping 192.168.1.1"
!com3:9600,n,8,1 connect to serial port com3 with settings 9600,n,8,1
!telnet 192.168.1.1 telnet to 192.168.1.1
!ssh pi@piZero:2222 ssh to host piZero port 2222 with username pi
!sftp -P 2222 jun01 sftp to host jun01 port 2222
!netconf rtr1 netconf to port 830(default) of host rtr1
!disconn disconnect from current connection
!Tab open a new tab
!Clear set clear scroll back buffer
!Prompt $%20 set command prompt to “$ “, for CLI script
!Timeout 30 set time out to 30 seconds for CLI script
!Wait 10 wait 10 seconds during execution of CLI script
!Waitfor 100% wait for “100%” from host during execution of CLI script
!Log test.log start/stop logging with log file test.log
!Disp test case #1 display “test case #1” in terminal window
!Send exit send “exit” to host
!Recv get all text received since last Send/Recv
!Selection get current selected text
Under The Hood
Command history is saved in %USERPROFILE%.FLTerm on Windows, $HOME/.FLTerm on MacOS/Linux by default, copy .FLTerm to the same folder as FLTerm executable for portable use. Since the command history file is just a plain text file, user can edit the file outside of tinyTerm to put additional commands in the list for command auto-completion. For example put all TL1 commands in the history list to use as a dictionary. In addition to command history, the following lines in the .hist file are used to save settings between sessions
~TermSize 100x40 set terminal size to 100 cols x 40 rows
~FontFace Consolas set font face to “Consolas”
~FontSize 18 set font size to 18
~LocalEdit Enable local edit
~WindowOpacity 80 set terminal window opacity to 80%
SSH know_hosts file is stored at %USERPROFILE%.ssh on Windows, $HOME/.ssh on MacOS/Linux. Password, keyboard interactive and public key are the three ways of authentication supported, when public key is used, key pairs should be copied to the same .ssh directory. id_rsa is supported by the Microsoft store version, which was compiled with winCNG crypto backend, id_rsa, id_ecdsa and id_ed25512 are supported on the apple app store version, which was compiled with openssl crypto.
scp and ssh2 tunnling funciton is integrated to the terminal, when a ssh connection is active, enable local edit mode and try the following commands:
!scp tt.txt :t1.txt secure copy local file tt.txt to remote host as t1.txt
!scp :t1.txt d:/ secure copy remote files *.txt to local d:/
!tun 127.0.0.1:2222 127.0.0.1:22
start ssh2 tunnel from localhost port 2222 to remote host port 22
!tun list all ssh2 tunnels
!tun 3256 close ssh2 tunnel number 3256
Apple store app is sandboxed, which means the home directory is isolated to “Library/Containers/com.github.tinyTerm2/Data”, both .ssh and .FLTerm are there, any file transfered without specifying local dir are copied to there. Note that even if a path is specified, access is most likely denied by the sandbox, even /tmp is not accessible.
To access the sandboxed home directory, the easies way is to type “!script $HOME” in local edit mode, which will open the sandboxed home dir in Finder, press “CMD+Shift+.” to see .ssh and .FLTerm