Manage file type and extension associations with the "assoc" command
This tool is very useful for managing the relationship or association between
file extensions and file types. the syntax is
the plain command "assoc" is entered, you will get a list of what
file types correspond to the extensions currently registered on the system.
The list can be quite long so it is best to redirect to a file or to pipe
to the "more" command
so that one full screen at a time can be viewed
assoc > list.txt or assoc
| more If the only parameter is a file extension (including the leading
period), the file type for that extension will be given. For example, to see
what file type is associated with .txt , enter
names used for the various file types may not always be obvious, the above
can be a useful type of command, In this case, the output would normally be
. To delete the file type association for the file name extension .xyz (use
assoc .xyz=Another use is to associate a given extension
with a certain file type.
As an example, to associate the extension .log with type txtfile,
assoc .log=txtfile Note that more than one extension
can be associated with a file type. For example, the file type "jpegfile" typically
has both the extensions .jpg and .jpeg associated with it.
Also note that it is possible to create your own file extensions and to associate
them with a filetype.
For a Microsoft reference on assoc go
here or to the Windows Help and Support Center. You can also enter.the
Manage file type and program associations with the "ftype" command
As previously mentioned, each file type has a set of operations and corresponding
software associated with it. In particular, all active file types have an
action named "Open" that is the default action. This is the action
that is invoked when you double-click a file with an extension associated
with the file type. There may also be other actions (listed in the Context
Menu) but ftype deals
The "Open" action
is defined by a string that includes the fully qualified path to the executable
file that is to carry out the action and any parameters
that must be passed to the executable. The syntax for ftype is
Entering the bare command "ftype" will list all of the current file types that have the open command strings defined and the corresponding command string. It can be quite a long list so it is best to redirect to a file or to pipe to the "more" command. Having the list can be convenient as a record of what programs are being used to open various files.
If a particular file type is specified,
then the command string for that file type will be displayed. Using the
text file type as an example, you would enter
would produce the output
%1This shows that the executable file that opens text files is notepad.exe located
in the folder \Windows\system32\ (The environment
variable %SystemRoot% is used
to indicate the Windows folder.) Note the presence of the placeholder %1.
This is necessary because the full command for the open action requires
the name of the file that is to be opened.and the placeholder stands for
the file name. This command is useful when you want to see what program
opens a particular file type.
If it were desired to change the openCommandString to use Wordpad
instead of Notepad, the command (on one of my computers) would be
txtfile="G:\Program Files\Windows NT\Accessories\wordpad.exe" "%1" (The
path for Wordpad will vary from one computer to the next. This example is
for illustration only). Note the use of quotation marks to enclose a path
with spaces in it. While changing
program associations may be easier using the Windows
Options dialog (no typing required),
the command line method can also be useful, especially in batch files.