OS/2 Shareware BBS: 8 Other/08-Other.zip/DEOS2.ZIP/ALIAS.DOC

Text File | 1988-02-22 | 9KB | 211 lines

                ALIAS

               Andrew D. Estes
               948 Sunridge Dr.
             Sarasota, Fl. 34234
                [phone]
            Compuserve 73076,2737



    As I began doing development work under OS/2 I suffered from a
loss of many of the utilities that I was accustomed to using under
DOS. Consequently one of my first tasks was to build OS/2 versions
of these programs.  This is the first of this set of OS/2 utilities.

    As this is a program that was written for educational purposes as
well as personal use, the documentation is sparse.  It assumes some
familarity with programs such as CED and with OS/2.  This must also
be considered an experimental program.  It has been tested, but I
would not consider it to be a production quality program by any
means.  This is not to imply that this may be a dangerous program
(OS/2 makes it very difficult to create a program that can damage the
system), only that the user interface is weak and that there may be
situations in which the program does not quite work as expected.  If
you should find any of the situations, please contact me and I will
try to correct the problem.

    This is a free program.  I am placing no restrictions on its use
or distribution.  I do ask that this document be attached so that
users will have a means of contacting me with problems.

    The ALIAS package consists of three files:

    ALIAS.DOC - this file
    ALIAS.EXE - the controlling program
    ALIAS.DLL - a dynalink library containing the alias subsystem.



                A FEW DETAILS

    ALIAS works by registering a replacement for the KBDSTRINGIN
function of the KBD subsystem.  This replacement function is
contained in the ALIAS.DLL file.  When a program calls KBDSTRINGIN,
the KBD function dispatcher notes that a replacement function has
been registered and directs the call there rather than to the
standard function.  This replacement function adds command recall,
command editing, and alias replacement to the normal KBDSTRINGIN.
There are two limitations to this approach.  First, a KBD replacement
function is only active in the screen group in which it was
registered.  This means that if you then switch to another screen
group, you will be using the standard (non-alias) KBDSTRINGIN
function.  Second, only one replacement function is allowed per
screen group.  If another process tries to register a new function,
OS/2 will fail the request.

    Since each session must register ALIAS, I decided that each
session should have its own recall stack.  This was implemented by
marking one data segment as nonshared.  Thus you should not expect to
be able to recall commands from one session while in another.  (In
future versions, I may decide to allow shared recall).

    On the other hand, I did not want to have to redefine aliases for
more than one session.  In this case, I defined the segment which
holds alias/replacement strings to be a shared segment.  If you
define an alias in session 1, that alias will be active in session 2
(assuming of course, that the ALIAS subsystem is active in session
2).

    Since ALIAS is a dynalink library, OS/2 must know where the DLL
file exists.  When loading a DLL, OS/2 looks along the path defined
by the LIBPATH variable.  When installing ALIAS, make sure that
ALIAS.DLL is put somewhere along this path.


            LOADING AND RUNNING ALIAS

    To load ALIAS, simply run ALIAS.EXE with no parameters.  This
will register the replacement KBDSTRINGIN function for the current
session (screen group).  If you run ALIAS.EXE a second time with no
parameters, you will receive an error message reporting the that the
function can not be registered.

    The base ALIAS system allows command recall and editing similar
to that found in CED.  I tried to follow the keyboard functions
defined in CED as much as possible.  All commands entered on the
command line are stored in a circular buffer.  These commands may be
recalled using the up and down arrow keys.  Command line editing is
also implemented.  The editing keys include:

   LEFT ARROW - move cursor left one character
   RIGHT ARROW - move the cursor right one character
   HOME        - move the cursor to the beginning of the line
   END         - move the cursor to the end of the line
   CTL-RIGHT   - move the cursor to the start of the next word
   CTL_LEFT    - move the cursor to the start of the previous word
   INSERT      - toggle insert mode
   DELETE      - delete the character at the cursor
   BACKSPACE   - delete the previous character.

    I also replicated the standard DOS/OS2 function key template
editing.  Note that these only work on the last command not on
recalled commands.
    Finally, CTL-PAGEUP will clear the recall buffer and CTL-PAGEDOWN
will remove the current line from the recall buffer.


    Command aliasing takes place when a line begins with a character
string that has been designated for replacement.  Such a string may
be recorded as follows:

    ALIAS cv cvp /43

The effect of this line will be that any time the KBDSTRINGIN
replacement function sees a line that begins with 'cv ...' it will
expand that line into 'cvp /43 ...' immediately before returning the
line to the calling program.  You will not see the replacement line
echoed to the screen, only the function that called KBDSTRINGIN will
see the expanded line.
    If you wish to record multiple aliases, you may create a file
containing the alias strings one per line.  To load the file invoke
ALIAS with a '-l filename':

    ALIAS -l alias.cfg

ALIAS will then read the file alias.cfg and record the alias strings.
You may clear the alias string buffer by invoking ALIAS with a '-c'
parameter:

    ALIAS -c

ALIAS will clear all defined aliases.  If you wish to redefine a
replacement string, simply enter the replacement as if it were a new
alias:

    ALIAS cv cvp /s

ALIAS checks each alias entered against all previously registered
alias strings.  If the source portion matches a defined alias, the
entire alias replacement string is replaced.  You may undefine an
alias by simply not having a replacement string:

    ALIAS cv

ALIAS sees that there is no replacement string and clears the 'cv
...' string from its alias buffer.  Finally, you may list all defined
alias replacement stings by running ALIAS with a '-l' option:

    ALIAS -l

ALIAS will then list to STDOUT (i.e. it may be redirected) all
defined alias strings.



                KNOWN PROBLEMS

    Since the ALIAS.EXE program terminates after registering the
KBDSTRINGIN replacement function, it is not possible to de-register
the function (OS/2 only allows the registering process to de-register
a replacement function).  This means that if you do not wish ALIAS to
be active, you must shut down the session in which it was loaded and
start another session without loading it.  As there are not as yet
many OS/2 programs, it is hard to determine if this is a real
problem.  I tend to think not.  The replacement KBDSTRINGIN function
will pass control back to the normal KBDSTRINGIN function if it does
not like the state of the keyboard or if it is called with a NOWAIT
option.
    As a side effect of the NONSHARED data segment, each process will
also have its own recall stack.  This is similar to the DOS and
APPLICATION command stack ideas of CED.
    Control character expansion is not performed.  Thus a tab
character is NOT expanded; in fact, a tab is simply ignored.  Other
control characters are displayed using the graphics characters rather
than the standard ^character form.
    The command recall buffer and the alias buffer are both set at
2048 characters.  These settings can not be changed.  The command
recall buffer is a circular buffer; earlier commands are simply
overwritten.  The alias buffer is simply a list.  If the buffer would
be overflowed by adding a new alias, the new alias will simply not be
accepted and you will receive an error message.
    ALIAS is a purely OS/2 program.  It does not work under DOS or
the DOS 3.x box.
    ALIAS has only been tested on the Microsoft SDK version of OS/2.
It should work on any other versions, but if not please let me know.


                FUTURE

    What is done with ALIAS in the future depends on any feedback I
receive on it.  If you would like additions, I am open to suggestion.
I may make changes to it and if they increase the functionality of
the program I will release the new versions.


               ACKNOWLEDGEMENTS

    It should be obvious that this program was heavily influenced by
the excellent program CED by Chris Dunford.  CED is one of those
programs that made working in DOS acceptable.  I only hope that this
program will be as half as useful.

    ALIAS consists of approx 2200 lines of assembler code for the
dynalink library and approx 200 lines of C code for the driver
program.  The program was written using the Microsoft OS/2 SDK.