Script to perform a web search in the user's default browser using the user's default search provider

default_search.sh

#!/bin/sh
# Script to launch a search in the user's default browser using their default
# search provider. (Best effort, given that
#
# There may be a ready-made way to do most of this, but I don't know it so I
# just implemented the spec.
#   http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

# Helpers for useful error handling
die() {
    xmessage "FATAL: $1" &
    exit "$2"
}
require() {
    if [ -z "$1" ]; then
        die "$2" "$3"
    fi
}

# Linux has `xdg-open <URL>` as an equivalent to `start <URL>` on Windows and
# `open <URL>` on OSX but, like those commands, it's completely confused by
# receiving `? <search term>` as an argument, so we manually figure out what
# command to call...

# Look up the .desktop application definition file associated with http:// URLs
xdg_name="$(xdg-mime query default x-scheme-handler/http)"
require "$xdg_name" "No association for http:// URLs" 1

# Since most Linux desktops have SOMETHING GTK+-based, we could normally just
# use `gtk-launch "$xdg_name" "whatever"` here and call it done for the vast
# majority of Linux desktops, but Firefox requires  --search rather than a
# leading ? and gtk-launch escapes that.

# Construct the search path
usrdata="${XDG_DATA_HOME:-$HOME/.local/share}"
sysdata="${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}"
data_dirs="$usrdata:$sysdata"

# Resolve the .desktop file name using the search path
OLD_IFS="$IFS"
IFS=":"
for datadir in $data_dirs; do
    candidate="$datadir/applications/$xdg_name"
    if [ -e "$candidate" ]; then
        found="$candidate"
        break
    fi
done
IFS="$OLD_IFS"
unset OLD_IFS
require "$found" "Could not find http:// URL handler: $xdg_name" 2

# Parse the raw command string out of the .desktop file
# (Not perfect, since it strips the % substitution placeholders rather than
#  obeying them, but perfectly fine for this restricted use case)
app_path="$(grep '^Exec' "$found" |
            head -1 |
            sed 's/^Exec=//' |
            sed 's/%.//')"
require "$app_path" "Could not parse Exec line from $found" 3

# Open browser, special-casing every browser I tested which didn't like "? ..."
case "$xdg_name" in
   *arora*) die "FATAL: Can't trigger default search provider in Arora" 4;;
   *firefox*) $app_path --search "$*";;
   *konqueror*) $app_path "$*";;
   *luakit*) $app_path "$*";;
   *midori*) die "FATAL: Can't trigger default search provider in Midori" 4;;
   *) $app_path "? $*";;
esac