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Welcome to MGW-LSH :
Lsh is a shell partially inspired by some command interpreters for PC
monitors (such as 4-DOS, DR-DOS, MS-DOS, N-DOS, PC-DOS, Q-DOS and
others, which might be trademarks of their owners and which is hereby
acknowledged). However, most of the features of this shell are simply
adapted from Unix (which also happens to be a trademark) shells.
Conditions :
You may only use, distribute and modify this package in accordance with
with the conditions of the GNU public license as set out in the file COPYING.
Quickstart :
If you want to try this shell without changing your login shell, try typing :
lsh -k
This will make that instance of lsh look like a login shell. Enjoy.
Lsh Features :
* Case insensitive builtins. "CD.." has the same effect as "cd .."
or "cD..". Environment references and file names are case sensitive though.
* Drive mappings : It is possible to map drive letters onto any
Linux path, for example "map d:=/home" will create (and delete any
previous definition of) a drive called "d:" which will have as its root the
"/home" directory. If no explicit mappings have been defined, then only
one drive ("c:") is created which is mapped onto the root directory. To
remove a mapping use "zap d:".
* Automatic conversion of switches : "tar /xvf d:\file.tar" will execute
"tar -xvf /home/user/file.tar" if "d:" has been mapped onto
"/home/user" and the variable "NOROOT" has been set.
* Aliases : For people who are too lazy to associate, say,
"/usr/bin/elm" with an interactive mail program, one can specify "alias
mail = "/usr/bin/elm"". To remove an alias, use the command "unalias".
Note that builtins like "dir" or arguments to builtins can not be aliased.
* Several commands on one line : A sequence of commands can be separated
by a ";". So "cls;dir" will clear the screen and then list the directory.
* Usable environment variables : "echo %HOSTNAME" will display the value
of the environment variable "HOSTNAME" if it is set.
* Crufty shell expansion : "w*w" will match "World" but NOT "we.will".
Essentially matching is case insensitive, but "*" stops matching when
encountering a ".". This may be a bit troublesome since Linux does not
have a one "." limitation in filenames. Some filenames such as
"a.file.with.lost.of.dots" will not show up in a normal dir listing,
you would have to go "dir *.*.*.*.*.*" to find it.
* No listing of special devices. Shell expansion will ignore any files
which are not directories or plain files. So a FIFO will not appear
anywhere. To observe this feature go "dir" in your "/dev" ("c:\dev")
directory. Files to which the shell has no access rights will also not
be included in the shell expansion. This has been specially built in to
protect novices from the shock of seeing new and strange files.
* Separate configuration files : A shell which is started by the login
program or which has the environment variable "NOUNINIT" set, will
attempt to read commands from "/etc/autoexec" and then from a file by
the same name in the users home directory (referencing the "HOME"
environment variable). At no stage is "/etc/profile" or ".profile"
read.
* Fascist restrictions : by setting the environment variables "NOALIAS",
"NOMAP", "NOUNINIT", "NOCHANGE", "NOROOT" and "NOSET" (in that order),
the user will not be able to set up any new aliases, map any new
drives, run an uninitialized shell, use the builtins which modify
files, use any Linux paths in commands or arguments, and modify the
environment. If one has mapped only a drive onto the users home
directory and set up suitable aliases and set the "PATH" variable to
".", it is possible to keep the user below his/her home directory and
deny any access to higher directories. At least that is the theory...
Please note that these restrictions were included to prevent novice
users accidentally compromising the system (since novice users, by
definition, are notorious for not logging out, choosing *really*
stupid passwords and the like, their accounts are liable to fall into
the wrong hands) and not to restrict experienced users... So it would
be nice for any sysadmin to change the shell of any user from this one
to a proper shell, if the user requests it.
* Limited size of the command line : The longest command which is
accepted by the shell may not exceed 127 characters.
* No real job control : It seems unfair to subject Unix haters to the
difficulties of managing tasks running in the background. A primitive
batch facility has been provided though : "sleep 20 !" will execute
"sleep 20" in the background and immune to hangups with output redirected
to "lsh.out".
* No real flow control : No commands for controlling the flow of a program
("IF", "DO", "WHILE", "FOR", "GOTO" are absent). It is cruel to
subject novices to programming. A minor concession has been
made, though, "?dir" will list the directory, but only if the
last external command was successful.
Builtins :
alias, break, bye, call, cd, chdir, cls, copy, ctty, date, del, dir,
echo, erase, exit, logout, map, md, mkdir, path, pause, prompt, quit,
rd, rem, ren, rename, rmdir, set, time, type, unalias, ver, vol, zap.
Have a look at the manual page for a more complete description.
Missing : As yet unimplemented
* Too few checks for excess parameters for builtin commands.
* No online help for builtins (dir /?).
* Too few bounds checks ;-).
A Couple of Warnings :
* Many of the builtin commands do not behave exactly in the manner you
would expect them to... Bear that in mind at all times.
* Reading the source might be hazardous to your health -- this little
program was written for relaxation during some serious exams. No
provisions for readability, efficiency, maintainability or any other y
were made.
A Crufty Problem :
* I did not feel like searching the command path manually, so if you
really need to run batch files do something like "call batchfile" or
"@batchfile" which also saves you spawning another shell, and retains
all current drive mappings (if you were to run a new instance of lsh,
you might have some different mappings, so some external commands
could be inaccessible). "call" is the only builtin which can take an
aliased argument, so you could go :
"alias batch="/usr/local/bin/batchfile""
to run file "/usr/local/bin/batchfile" containing lsh commands through
the current lsh interpreter if you type "@batch". Of course you can
use the usual Unix script way if you do not mind having another new
shell around.
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