xdg-override: change default application temporarily on Linux

I just have a small shell script as "xdg-open". Writing this was easier than figuring out the magic xdg-* tools use the figure out the default application for something, and then not having that work on random days for reasons of planetary alignments.

This is not that different from "xdg-override"; you can add global overrides for specific URLs with a simple match, and matches from a specific application by checking the parent process (e.g. $(readlink /proc/$PPID/exe) = /usr/bin/slack, or some such). It seems easier to me to have everything in one place.

I also considered popping up dmenu for unknown filetypes, but I don't use it that much and don't really need it.

At any rate, "to whom it might be useful":

  #!/bin/zsh
  #
  # xdg-open, without suckage.
  [ "${ZSH_VERSION:-}" = "" ] && echo >&2 "Only works with zsh" && exit 1
  setopt err_exit no_unset pipefail
  
  (( $+1 )) || { print >&2 'need a parameter'; exit 1 }
  
  # Open URL.
  if [[ -z "${1:#*://*}" ]]; then
   proto=${(L)1%%://*}
   case $proto in
    (http|https)   exec firefox $1 ;;
    (file)      
     1=${1##$proto://} # Remove protocol
     1=/${1#*/}        # Remove hostname
    ;;
    (*)
     print >&2 "xdg-open: no URL handler for protocol '$proto://' (for: $1)"
     exit 1
   esac
  fi
  
  # Open file.
  ext=${(L)1:e}
  case $ext in
   (html|htm|pdf)                                  exec firefox   $1 ;;
   (png|webp|jpg|jpeg|heic)                        exec firefox   $1 ;;
   (mp?|ogg|flac|m4v|mkv|avi|mov|wav)              exec mpv       $1 ;;
   (md|markdown|txt|sh|zsh|go|py|rb|js|c|json|xml) exec st -e vim $1 ;;
   (*)
    mime=$(file -b --mime $1 2>&/dev/null ||:)
    t=${mime%/*}
    case $t in
     (text)        exec st -e vim $1 ;;
     (image)       exec firefox   $1 ;;
     (audio|video) exec mpv       $1 ;;
    esac
    print >&2 "xdg-open: don't know how to open '.$ext' files (mime: '$mime') (for: $1)"
    exit 1
  esac

On gnome there is a GTK4 app called "Junction". It pops up a dialog that let's you choose what application to open the given content in. I highly recommend just aliasing 'open' to use that.

https://apps.gnome.org/Junction/

I don’t understand those comments. I’ve been using sway for years, i3 before that and I’ve been using xdg-open since forever to open any file in the default application and I never felt it was confusing or I that I needed to replace it with something else. What am I missing?

IMO PATH-prepending is the right (unix-y) way to override certain commands, as OP does.

but sadly, many projects, programms which I came across (mostly but not exclusively daemons), defines PATH for themself, not respecting inheritence: saying "what if someone set it up maliciously" or "default PATH is not enough / too wide / in wrong order / etc" ...

man, sorry, process! what you inherit is what there is, it's your environment where you need to do your job. you can't? just fail and let the caller know the error case. will you (as an app author) change the CWD because it's unfamiliar (breaking relative path parameters along the way)? or redirect STDERR from a file to tty because "user MUST SEE this error" (making it NOT shown in the error log where the user did want to put the error output)? no. that's why you should not touch PATH. except if you are a logon process, a wrapper whose responsibility is to prepare the env for descendents, or crossing privilege boundary.

due to this defiance of many programms, I started to switch from PATH-prepending to "over-mount executables in separate mount namespace" strategy. I hope it won't be voided by they invent "let's switch to the default namespace because it's my will" type of overreach.

> Override xdg-open behavior. Because the way it already works is not confusing enough.

Oh! YESSSSS!!! FINALLY!!! I've been removing x permissions for xdg-open for YEARS!!! I hope this works.

That reminds my of a own xdg-open I wrote that sits in /usr/local/bin/xdg-open.

It's a simple python script that checks by looking at the protocol, mime type or extension which URL it is and also asks if there are multiple applications

https://paste.sr.ht/~fossdd/7fa65e10998ebcc03a2bbcc8488f94e9... (CC0)

My work VPN client doesn't work in Firefox, so I hacked something much more specific together to deal with that problem

  #!/bin/sh
  
  if [ "$@" = "/tmp/gpauth.html" ]
  then
    flatpak run --filesystem=/tmp/gpauth.html org.chromium.Chromium /tmp/gpauth.html
  else
    /usr/bin/xdg-open "$@"
  fi

joining to the "everyone reimplements a file-opener" team (shameless plug) : https://github.com/bAndie91/mimeopen-gui

Is this like the "open with" option in Windows?

Who would win customxdgoverridebinary application .ext

or just

application file.ext

Some people just really take any excuse to write a program.