About "shEdit"
--------------
shEdit is a minimal text editor written in POSIX shell. It's inspired by the
GNU Nano editor, but is even more minimalistic. I created it mostly for "fun",
but it could be useful in situations where you can't use your favorite text
editor, for instance:
* If you need to use some system where no sane text editors are installed
(or perhaps, you really don't like "vi").
* Special constrained environments such as an over a serial line or in an
initramfs/initrd, where a normal editor might not work properly.
* If you need a minimalistic portable text editor.
Current status and bugs
-----------------------
Not everything is working yet:
* Long lines can't be displayed properly and will usually be truncated.
* No UTF-8 support.
* Search does not work.
* No word navigation.
* Lines containing capital letter U with circumflex gets filtered due to a
bug (technically, this happens because it contains the escape character
0x9B in it's UTF-8 encoding).
* No save or overwrite prompt (currently, files can't be overwritten)
Limitations of shell script
---------------------------
shEdit uses shell variables named file_row1, file_row2, and so on to store the
text buffer. This is of course not very efficient for files with many lines, or
when a line is inserted or deleted in the middle of the file. The latter
can be improved to some degree, by deferring the insertion or removal of
off-screen lines, so multiple lines can be "moved" at once.
Some shells or systems may impose limits on the number or total
size of variables, so that will limit the size of the files you can edit with
shEdit. Additionally, shell variables generally don't allow null bytes, so
don't try to edit binary files! (Also, shEdit will strip escape characters,
but that's a limitation of shEdit and not of the shell)
Also, proper UTF-8 support will require special handling for different shells.
Most shells simply treat strings as byte arrays (which is much more flexible).
But Bash 4 and later treats multibyte characters as single units, so it will
need special handling when adding UTF-8 support.
Finally, there's no standard way of reading a single key store in POSIX shell,
and you can't turn off character echo either. So shEdit will try to use
external commands for this.
System requirements
-------------------
As long as you only edit small files it shouldn't require much of your system.
The software requirements are:
- sh (POSIX compatible, tested with dash, bash, zsh, ksh, ksh93, mksh)
- dd (or head. not required under bash)
- Linux console or xterm-like terminal (might work under other VT100
terminals as well)
It's also very much recommended to have "stty" installed. Otherwise, key
strokes will be line buffered, so you'll have to press ENTER after to actually
send your key strokes to shEdit (but shEdit has been tested to work in this
mode also). Without stty, shEdit will also assume that the terminal size is
80x24.
In line buffered mode ("broken input mode"), you may not be able to use
all Ctrl-<key> commands. Instead you may press ESC ^ <key> (where ^ is the
circumflex/caret character).
shEdit doesn't use terminfo, and uses hard-coded escape sequences instead.
So it might not work on all terminals, but it has been tested to work on
lxterminal, xterm and Linux console.
Warning
-------
This script uses eval to read files. If there would be a bug in this code then
this could lead to a security issue. It could also trigger the "Bash bug", I
guess, if a line starts with (). Also, not all escape sequences are cleaned
before displaying the text on the terminal.