Default Applications (MimeTypes)

TL;DR: how to “revert” messed up default application after installing brave (or any other app that fucks up mime type associations)

the story

Yesterday I had the great idea of installing brave on my machine. Not because I want to use it, but I want to “test” it.

It worked, it launched, it asked if I want it to be my “Default Browser”, no! (I am 98,765% sure, that I clicked on “NO”) … everything was fine. I went to bed.

but

Today I wanted to open a PDF, using xdg-open. Surprise: the PDF opened in brave. Ok, stupid, lets fix it.
So I opened up the “Default Applications”-Settings on XFCE.

WTF

brave is set as default Browser,
brave is set as default PDF-Viewer,
brave is set as default Image-Viewer,
brave is set as default fuckin’ (almost) everything!

After deleting or resetting some entries in the Settings GUI I found, that they get marked as modified and setting them to default (re)sets the entries to brave …

Suspicious!

So I have read a little bit about how “Default Application”/“Default MimeType”-handling worked.

Then I wrote a little Shell Script to find all locations of interest.

The script generated a report, then I manually “fixed” all files and regenerated the mime caches.

voila

The mess is gone!

the background

Default Applications based on Mime Types works in a quite clever way on Linux.

First, there are .desktop-files. They contain information like the icon for the UI, the command to be executed when run, … and a list of MimeTypes, which can be opened by the app.

Second, there are mimeinfo.cache files. These are generated files, the command update-desktop-database reads all .desktop files and populates them. They are the base for handy “Default Application”-UIs.

Last but not least, there are some default app .list files. Some for system defaults (in /usr/...), some for “admin” defaults (in /etc/...) and some per user (in $HOME/.config/... or $HOME/.local/...). These files are what you can edit via the “Default Application”-UI.

Most of the known MimeTypes had no assosiated application (why would I wan’t to have an application for “Windows App Store Installer”, …?) and I don’t want brave to populate those empty entries.

So I had to delete them in a way, that update-desktop-database would not regenerate .list files with brave.

Easier said than done. I was in desperate need of a bash script reporting all these locations. (the brave installer put brave in lots of places.)

the script

#!/usr/bin/env bash
set -euo pipefail

DEFAULT_APP_FILES=( \
    "$HOME/.config/mimeapps.list" \
    "$HOME/.local/share/applications/mimeapps.list" \
    "/etc/xdg/xfce4/helpers.rc" \
    "/etc/xdg/mimeapps.list" \
    "/usr/share/applications/mimeapps.list" \
    "/usr/share/applications/defaults.list" \
    "/usr/local/share/applications/mimeapps.list" \
    "/usr/local/share/applications/defaults.list" \
)
DESKTOP_FILES=( \
    "/usr/share/applications/brave-browser.desktop" \
    "/usr/share/applications/brave-browser-beta.desktop" \
    "/usr/share/applications/brave-browser-nightly.desktop" \
    "/usr/share/applications/com.brave.Browser.desktop" \
)
MIME_CACHE_FILES=( \
    "/usr/local/share/applications/mimeinfo.cache" \
    "/usr/share/applications/mimeinfo.cache" \
)

do_report() {
    # usage:
    #     do_report  TITLE  PATTERN  ARRAY
    # where:
    #     TITE      is the title.
    #     PATTERN   is whatever you want to look for (f.e. brave)
    #     ARRAY     is an array of filenames to check
    local TITLE=$1
    local PATTERN=$2
    shift 2  # "skips" the first 2 arguments
    printf '\n## Common "%s"\n\n' "$TITLE"
    printf 'Search Pattern: `%s`\n\n' "$PATTERN"
    for FILE in "$@"; do
        if [ -f "$FILE" ]; then
            printf '### %s\n\n' "$FILE"
            MATCHES=$(grep -i "$PATTERN" "$FILE" || true)
            if [[ "$MATCHES" != "" ]]; then
                printf '```plain\n'
                printf '%s' "$MATCHES"
                printf '\n```\n\n'
            else
                printf 'Pattern not found.\n\n'
            fi
        fi
    done
}

printf '# fu-brave report\n'

do_report "Default-App Files" brave "${DEFAULT_APP_FILES[@]}"
do_report ".desktop Files" "MimeType=" "${DESKTOP_FILES[@]}"
do_report "MIME-Cache Files" brave "${MIME_CACHE_FILES[@]}"

printf '# Next Steps\n\n'
printf 'Clean Up whatever you want to clean up; then do:\n\n'
printf '```\n$ sudo update-desktop-database\n```\n'

fu-brave.sh (this bash script, on codeberg.org)

Thanks for Reading :-)