ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/UTILITY/DIR/WHICH20.ZIP/WHICH.DOC

Text File | 1990-01-02 | 10.5 KB | 256 lines

                                 WHICH, v2.0
                                -------------
                                from TifaWARE




What's New
----------


     New to version 2.0 is a verbose reporting option; with it you see
exactly which directories are being searched. Additionally, several of the
main functions in WHICH have been rewritten, and AT&T's getopt() function
is now used for a consistent method of option processing. Finally, memory
problems at run-time should be a thing of the past as directory names no
longer require additional memory allocation.

     Version 1.2 of WHICH does not represent much of an improvement over
the preceding release, at least from the user's viewpoint. Some of the code
for displaying the on-line help message was improved, and error messages
are formated in a slightly different fashion. Also, program names are not
converted to uppercase if no match is found.




Introduction
------------


     With the increasing popularity and size of hard disks, keeping track
of executable programs is becoming more and more difficult.  If you're like
me, you probably have a few programs on your disk with the same filename,
possibly even some in the same directory.  Which one will be run when you
type the command's name at the DOS prompt?

     The answer, of course, depends on your current directory as well as
the setting of the PATH environment variable.  When you type a command at
the DOS prompt and press <ENTER>, DOS determines if the command is internal
or external.  Internal commands - CLS, DIR, COPY, etc... - are implemented
within DOS itself; external ones are disk files with an extension of COM,
EXE, or BAT.  First, DOS compares your command against its list of internal
ones.  If no match is found, DOS assumes the command is external and tries
to find the program on disk.  It looks in the current directory for a file
with the same filename as the command and an extension of COM, EXE, or BAT
in _that_ order.  If DOS is still unsuccessful, it then continues to search
sequentially through the directories specified by the environment variable
PATH until a match is found.  Only if DOS runs out of directories to scan
does it print the dreaded "Bad command or file name" message.

     As the name suggests, WHICH searches your system for programs that
MS-DOS is capable of running.  It is not a general file-search utility a la
PKFIND or WHEREIS; rather, it scans only a few directories for executable
programs or batch files.  But it can save a lot of frustration if any of
your programs have the same names.




Usage
-----


     Running this program is straightforward.  Once you've placed WHICH.COM
on your disk where DOS can find it (either in the current directory or one
specified by PATH), you're ready to use it.  Type WHICH -? and you'll see a
message similar to the following:

     TifaWARE WHICH, v2.0, Jan 02 1990 - scans path for executable programs.
     Usage:  which [-options] prog(s)

     Options:
       -a = find all possible matches
       -v = verbose reporting
       -? = provide this help message

     Prog(s) must not contain wildcards or drive/path/extension info.

[If you don't remember anything else from reading the documentation, at
least remember how to display this help message.]

     To search for one or more files, simply add their filenames to the
command line when you invoke WHICH.  [Note: Only "filenames" are accepted
as arguments; i.e., that part of a file's name located between the drive
and path specifiers on one hand and the extension on the other.  For the
file named "C:\AUTOEXEC.BAT", the filename is "AUTOEXEC".] Suppose you want
to determine which versions of GREP, WP, and DV will be executed by DOS.
Then you could simply type "which grep wp dv".  On my system, this produces
the following output:

     C:\BIN\GREP.EXE
     which: no matches for wp.
     C:\USR\BIN\DV.BAT

Notice that when reporting matches, WHICH converts filenames to uppercase
regardless of how they are specified on the commandline.  MS-DOS does not
distinguish between upper- and lower-case letters in filenames; neither
does WHICH.

     You can force WHICH to search all directories in the path by using the
'a' option. What good is this? For one, it's a way of locating extra copies
of programs and freeing up vital disk space. You'd be surprised how many
people keep two or three copies of COMMAND.COM, for example, on their hard
disk! For another, this option can help determine why a particular program
exhibits different behaviour depending on where you are when it's invoked.
Rather than pulling out all your hair you might discover two distinct batch
files with the same name but in different locations on your hard disk.

     The 'v' option is primarily designed for debugging purposes. It simply
enables verbose reporting of WHICH's progress through each directory. With
this option you can tell exactly which directories are being searched. As a
bonus, you'll see if any tricks were used to name a directory (like hidden
characters!) since each name should end with a backslash.

     When WHICH is successful, it writes a program's complete file name to
standard output.  Using the DOS redirection characters '>' and '|', you
could send this ouput to a disk file, printer, or even use it as input into
another program.




If You Have Any Trouble
-----------------------


     WHICH will either report the full file names for the programs you
specify on the command line or notify you of a problem.  Here are the error
messages you might see and how you should deal with them:

     which: illegal option -- x.
          - Type "WHICH -?" for a list of valid options. If your
            program's name starts with a '-', you can avoid
            having WHICH treat the name as a set of options by
            preceding it with another name. For instance, typing
            WHICH AUTOEXEC -ODDNAME would search for the program
            -ODDNAME as desired.

     which: can't determine directories to search.
          - WHICH can't figure out the default directory perhaps
            because of trouble with the current drive.

     which: invalid filename -- c:progname.
          - Look back at the definition of a filename. It must
            not contain any drive, path, or extension information
            *nor* wildcards.

     which: no matches for progname.
          - Check the setting of PATH, the current directory, and
            the spelling of the program's name. Or perhaps the
            program simply doesn't exist on your machine.

These error messages are written to the standard error device.  In this
way, they won't disappear down a pipe or into a file should you try to
redirect WHICH's output.

     Additionally, WHICH uses a return code to convey information about the
success or failure of its searches.  Possible return values are:

     Code      Meaning
     ----      -------
     0         Matches were found for all program names
     1         Help message was displayed
     5         WHICH could not determine which directories to search
     10        At least 1 program name could not be matched
     20        At least 1 program name was an invalid filename.

You can test for these codes using the ERRORLEVEL variable in a batch file.

     Finally, it should be noted that WHICH limits processing to 25
directories; it will simply ignore any others listed in your PATH. If this
is a problem for you, you can either reorganize your hard disk or change
the constant MAX_DIRS in the source and recompile. I strongly recommend
the first course of action.




Requirements
------------


     TifaWARE WHICH runs on machines operating under MS-DOS v2.xx or later,
and requires roughly 10K of memory.  It does not use BIOS calls, make
direct writes to video RAM, or otherwise require machines to be
"PC-compatible".  In fact, WHICH even runs properly on a DEC Rainbow!

     WHICH makes no attempt to work with any command aliasing utilities or
path-extenders for the PC; eg, ALIAS, SEARCH, GLOBALS, ...  If you try to
use it with one of the former, WHICH will probably report no matches; with
one of the latter, probably a match in the current directory regardless of
how PATH is set.




Who Owns WHICH?
---------------


     I am releasing this implementation of WHICH into the public domain.
Since my involvement with MS-DOS began in 1984, I've been a heavy user of
public domain software (especially Kermit and a host of utilities for the
DEC Rainbow).  Public domain software is a terrific idea.  For the most
part, programs are useful and the source code instructive, all at no cost!
With this small contribution to the public domain I hope to pay back, in
some sense, my gratitude to those other programmers who have made my
computing so much easier.

     As a public domain program, WHICH carries no obligation on my part to
support users or provide future upgrades.  I have tried to write clean code
and believe it to be for the most part "bug-free".  Nevertheless, you must
use this program ***AT YOUR OWN RISK***.  I strongly urge you to scan the
source code yourself, make any desired changes, and recompile the program,
if this is possible.  If you make this standard practice with newly
acquired public domain software, you'll not only protect your system from
worms and viruses but also get a better feel for exactly how each program
works!

     As author of WHICH, I ask of you two things: First, if you distribute
this program, please keep together my original source code, documentation,
and executable.  This just makes it easier for others to use the software.
Second, let me hear what you think of WHICH.  You don't have to send any
money, just comments and suggestions.




Kudos
-----


     The idea for WHICH came to me while reading _The UNIX Programming
Environment_ by Kernighan & Pike.  The code itself was written using
Borland's TURBO C, v2.0.  I've seen several implementations of WHICH
already in the public domain, but I wanted to try out TURBO C's integrated
development environment.  Not bad!





                          George A. Theall

                             TifaWARE
                       506 South 41st St., #3M
                      Philadelphia, PA.  19104
                              U.S.A.

                          [phone]

              [e-mail] (ARPA Internet)