How do I change the MIME type for a file?

I have a file that is formatted as a .doc, but Nautilus and LibreOffice insists that it is a .txt. Both precise and Ubuntu 12.10 are that way, but Google Docs can convert it (after playing with it).

3 Answers

To check if 'extension' mime type exist:

grep 'extension' /etc/mime.types

To create new mime type:

1. Open /etc/mime.types with text-editor(with root privileges)

   gksudo gedit /etc/mime.types

2. Add extension to /etc/mime.types in following format:

   text/extension extension

For more info click here

Could be something as simple as a mangled/intentionally changed header. Here's what the MS Word first 2 chunks looks like in a couple of documents I just checked:

D0 CF 11 E0 A1 B1 1A E1

You could MAKE A BACKUP and try changing the first several bytes to that signature and see if it doesn't at least TRY to open as the right thing.

Generally, file can look at this area:

And tell the file-type. If it's detecting it wrong, either it actually is a text file renamed to doc or the header got borked.

1. In Nautilus, right-click on any file with the desired filetype or extension, choose Properties from the context menu.
2. In Properties click on the Open With.
3. Select an application for the given filetype (writer I asssume). All files with the same extension will now be opened with this program by default.

You can do this manually too

• /usr/share/applications/defaults.list holds the defaults (ie. system wide associations).
• ~/.local/share/applications/mimeapps.list holds user specifics.

By the way: I assume you have software installed (ie. LibreOffice) that can open doc files?

From the comments and images added:

• it could be that the file is corrupt. What a file is is based on the 1st byte of a file (and not the extension as Windows does). What you could do is set .txt files to open with Writer (just temporary) and see if it then does open and then save it under another name. Then reset opening txt to Gedit or what it was before.