I'm looking at a batch file which defines the following variables:
set _SCRIPT_DRIVE=%~d0 set
set _SCRIPT_PATH=%~p0
What do %~d0 or %~p0 actually mean? Is there a set of well-known values for things like current directory, drive, parameters to a script? Are there any other similar shortcuts I could use?
%~d0 gives you the drive letter of argument 0 (the script name), %~p0 the path.
They are enhanced variable substitutions. They modify the %N variables used in batch files. Quite useful if you're into batch programming in Windows.
%~I - expands %I removing any surrounding quotes ("")
%~fI - expands %I to a fully qualified path name
%~dI - expands %I to a drive letter only
%~pI - expands %I to a path only
%~nI - expands %I to a file name only
%~xI - expands %I to a file extension only
%~sI - expanded path contains short names only
%~aI - expands %I to file attributes of file
%~tI - expands %I to date/time of file
%~zI - expands %I to size of file
%~$PATH:I - searches the directories listed in the PATH
environment variable and expands %I to the
fully qualified name of the first one found.
If the environment variable name is not
defined or the file is not found by the
search, then this modifier expands to the
empty string
You can find the above documented in "FOR /?".
The magic variables %n contains the arguments used to invoke the file: %0 is the path to the bat-file itself, %1 is the first argument after, %2 is the second and so on.
Since the arguments are often file paths, there is some additional syntax to extract parts of the path. ~d is drive, ~p is the path (without drive), ~n is the file name. They can be combined so ~dp is drive+path.
%~dp0 is therefore pretty useful in a bat: it is the folder in which the executing bat file resides.
You can also get other kinds of meta info about the file: ~t is the timestamp, ~z is the size.
Look here for a reference for all command line commands. The tilde-magic codes are described under for.