_____USAGE

MYCD  [[$env_var] [d:][path/]directory]

_____DESCRIPTION

MYCD is an alternative to the MS-DOS(tm) cd command that offers shortcut ways
to change the current directory [or drive].  MYCD interprets wildcards, 
forward and reverse slashes, dots, environmental variables, and will use a 
variable CDPATH, if defined, to direct its search pattern for a directory.

An environmental variable is given by preceding it by a '$' or a '%'.  For
example, if there is an environmental variable SRC,  "MYCD $src"  (or 
"MYCD %src" ) will change to the directory defined by SRC.  An environmental
variable can precede a path ( "MYCD $src/pa*" ), but any '$' or '%' will be 
interpreted literally when interior to the path.

MYCD will deal with a drive request ( "MYCD d:..." ) by actually changing to
the drive specified.  This is different than MS-DOS's cd behavior, where
under the same circumstances, the current directory on the drive is changed,
but the present working directory remains the same (no drive change).

After dealing with the drive information, MYCD has the same notion of 
`absolute' or `relative' changes of directory as does the MS-DOS cd.

If the path requested, after being stripped of any drive information, begins
with a slash, then the path change is interpreted relative to the root
directory.  Thus, the following absolute changes are determined:
  MYCD \path          change to \path on current drive
  MYCD d:\path        change to \path on drive d:

The alternative is that the path is considered as a relative path.  If an
environmental variable CDPATH is _not_ set, changes are made relative to the
current directory.  For example, "MYCD dog" will change to the subdirectory
dog of the current directory, if there is one.  General examples (with "path"
having no leading slash):
  MYCD path           change to path relative to current dir, on current drive
  MYCD d:             change to current dir on drive d:
  MYCD d:path         change to path relative to current dir on drive d:
  MYCD [no args]      change to root dir (\) on current drive (an exception)

If an environmental variable CDPATH is specified (e.g., with the MS-DOS SET
command), MYCD's changes relative to a current directory are modified.  That
is, MYCD will deal with `absolute' paths having a slash at the beginning, or
paths beginning with an environmental variable, just as described above,
but will deal with other paths relative to the contents of CDPATH.  

CDPATH is a list of paths, delimited by ';', similar to PATH.  For example, 
    "set CDPATH=.;\;c:\;e:\upload;..;h:\work".   
MYCD will successively treat each of the paths specified as the current
directory, and try to change relative to that directory.  For example, with
the above CDPATH,   "MYCD rep*/d*"   will change to h:\work\reports\daily
if h:\work is the first entry with a subdirectory name matching the pattern
"rep*/d*".  A judicious setting of CDPATH is very valuable; note that it is 
the PARENTS of frequently accessed paths that should be specified in CDPATH.
For example, the choice "e:\upload" above, should mean that you wish to 
access various subdirectories of e:\upload by name, not that e:\upload is
frequently accessed.  It would be strange to have anything other than '.' 
as the first entry in CDPATH, so be sure to do this!  

MYCD allows wildcards '*' and '?' throughout the path.  These are interpreted
in the MS-DOS style and a change will be made to the first matching directory
found by MS-DOS (no attempt is made to resolve ambiguity).  For example, if
you have subdirs bat, batch, backup, bad.dir and you issue "MYCD ba*d*" you
can land in any of these except bad.dir.  (This is what MS-DOS function calls
do (sigh).  If you are confused, look up wildcards in your MS-DOS manual.)

MYCD deals equally well with forward and reverse slashes.  It will reduce
multiple consecutive slashes to just one slash.  It also understands "." as
the current directory and ".." as a parent, when delimited anywhere in a
given path.  Thus "MYCD cow\dog//./\\..\/cat\"  is equivalent to  
"MYCD cow\cat".  As a  bonus, 3 dots mean grandparent directory (e.g., 
"MYCD c:\x\y\z\..."  <->  "MYCD  c:\x"  or  MYCD e:...  <->  MYCD e:../..  ),
and 4 dots for great-grandparent,...

MYCD sets the MS-DOS errorlevel to 1 if it fails to change directory.  MYCD
does not print anything unless an error occurs.

_____HINTS

Copy MYCD.com to a ramdisk (d:\ say) at boot time and use an aliasing to make
cd a synonym for d:\mycd.  (Since the surrogate cd command will not be part
of command.com, you want it to load and execute as quickly as possible.)

It is not a good idea to put into CDPATH any path that begins with a floppy
drive that is sometimes empty:  you have instructed MYCD to look there.  If
you get the "Not ready error reading drive X" message while executing MYCD,
processing will be aborted unless you put a valid disk in the drive and
retry.

A request "MYCD $dirname" with the intent of changing to a directory whose
name begins with '$' will fail.  If you actually give directories names
beginning with '$' or '%', hide this from MYCD.  For example, use
"MYCD ./$dirname".

_____BUGS and LIMITATIONS

Resolution of wildcards can cause some surprises.  If subdir aaa has subdirs
bb1 and bb2; and bb2 has subdir cc3, the request "MYCD a*/b*/c*" may or may
not work, depending on the directory ordering maintained by MS-DOS.  The path
may expand as aaa/b*/c* to aaa/bb1/c*, for which there is no match; or it may
expand as aaa/b*/c* to aaa/bb2/c* to aaa/bb2/cc3.  I don't think that the
extra complexity needed to deal with the generality of situations like this
is warranted.

Environmental variables are treated as upper case, which is normal for
MS-DOS.  For example, "set src=f:\srcdir" actually stores an environmental
variable named SRC.  If you use some utility and put mixed case in
environmental variables, MYCD will not find these.

When an environmental variable is specified as the initial part of an
argument, MYCD does not use CDPATH.  For example, "set up=.." and "MYCD $up"
will operate, but "set b=b*" and "cd $b" will look for a directory "./b*",
which isn't very useful.  The lesson here is to use environmental variables
that specify a relative motion or include drive and complete path.

The number of characters in the full name of the path of the new directory
cannot exceed 127 characters.  CDPATH cannot contain more than 191
characters.  Results are unpredictable if these limits are exceeded.

MYCD says its name as "cd" in error messages, regardless of what you call it.

_____AUTHOR

J. Martin Borden
att!granjon!marty   or   marty%garage.att.com

There is no warrantee, expressed or implied, with this distribution.