Bernd Eggink

Linux default browser / Java

Some desktop systems know the concepts of "default browser" and "default mailer", programs that are launched automatically if URLs with certain protocols (http, https, mailto) are to be handled. These notions are of interest, among others, for Java programmers.

Java: In Java 6 the class Desktop supplies an API for launching (among others) the default browser and mailer in a system independent way. So much for theory. While this works fine under Windows and MacOS, it is not guaranteed to work under Linux or Solaris. Here Java 6 relies solely on the existence of a set of GNOME libraries. If they are missing, the Desktop API won't work. This means that on pure GNOME systems the API will be supported, while on others you may have to install some additional packages. Unfortunately the documentation doesn't say which libraries Java 6 is looking for. My experiments showed that at least libgnome and gconf are needed, probably others required by these as well. On pure KDE systems these libraries will likely not be present, so if you want to utilize the Desktop there, you'll have to install the corresponding rpm packages. ^[1] Furthermode, it appears to be necessary to assign a default browser and mailer once to make the whole thing work. file: URLs are not passed to the browser.

Browser/mailer coupling: Apparently not only Java, but also the family of Mozilla products uses the GNOME mechanism (at least with Firefox 3). Thus the presence of the libraries has an additional advantage: Clicking on a mailto: link in Firefox automatically activates the default mailer, and clicking on a http link in Thunderbird activates the default browser, both without the need to change any options in the prefs.js files.

Setting: The default browser may not always be the one you want. On some desktop systems the defaults can be set via the GUI. If there is no such facility, one could try to change the setting by the program itself, for example, let Firefox make itself the standard browser. But this also doesn't work in all cases. However, there is always one last resort: The program gconftool-2, which is part of the gconf package. It allows assigning a default application to every single protocol (http, https, mailto etc.). Exactly for this reason it isn't very convenient. The following scripts stdbrowser and stdmail provide a more comfortable tool for changing the default settings. The latter is simply a symbolic link to the former.

Usage:

stdbrowser -h Print a short help

stdbrowser -p Print path of the default browser

stdbrowser -s path Set the default browser. If path is a simple name, the program is looked up using $PATH.

stdbrowser -k Kill a running default browser (if it hangs).

stdbrowser URL Launch the default browser with the given URL.

If called with the option -s, the script assigns the new browser to all appropriate protocols (http, https, ftp, chrome). If the same script is called as stdmail, everything said above refers to the default mailer. Here a mail address is supplied with the optionless call. The default mailer is assigned to the protocols feed, mailto, news, nntp, snews.

Option -k can be used if the program hangs and can't be kill by means of the GUI (a well-know browser misbehaviour). The script issues the rather brutal command pkill -KILL name, where name is the base name of the program.

The optionless call simply means an indirect start of the default application. This may add some flexibility to your system. For example, you could use stdmail (instead of Thunderbird) as the application handling "mailto:" links in Firefox. If the default mailer is changed afterwards, Firefox will use the new setting immediately, without its configuration having to be changed.

For installation, unpack the script in an arbitrary directory. Go to this directory and create a symbolic link using the command

ln -s stdbrowser stdmail

Called under the name stdmail, the script will handle the default mailer.

#!/bin/bash

function getCmd     # protocol
{
    local out=$(gconftool-2 -g /desktop/gnome/url-handlers/$1/command)

    echo ${out% *}
}

#-----------------------------------------------------------------------

function usage  
{
    echo "Usage: stdbrowser option [path]"
    echo "       stdbrowser [param]"
    echo "Options:  -h      This help"
    echo "          -k      Kill a running application"
    echo "          -p      Print current path"
    echo "          -s      Make 'param' the standard application"
    echo "          -t      Test (output command)"
    echo
    echo "Without option h,k,p,s: run standard app with param"
}

#-----------------------------------------------------------------------

while getopts "hkpst" opt
do
    case $opt in
    (h)     usage
            exit 0
            ;;
    (k)     killit=1
            ;;
    (p)     prt=1
            ;;
    (s)     setpath=1
            ;;
    (t)     T=echo
            ;;
    (*)     usage
            exit 1
    esac
done

type gconftool-2 >/dev/null || exit 1

shift $((OPTIND - 1))

name=${0##*/std}
base=/desktop/gnome/url-handlers

[[ $killit ]] &&
{
    # kill if running

    if [[ $name == browser ]] 
    then
        exec pkill -KILL $(basename $(getCmd http))
    else
        exec pkill -KILL $(basename $(getCmd mailto))
    fi
}

[[ $prt ]] &&
{
    # no parameter, print current

    if [[ $name == browser ]]
    then
        getCmd http
    else
        getCmd mailto
    fi

    exit 0
}

param=$1

[[ $setpath ]] &&
{
    # make param absolute

    if [[ $param != */* ]] 
    then
        param=$(which $param) || exit 1
    elif [[ $param != /* ]] 
    then    
        param=$PWD/$param
    fi

    # change gconf commands

    if [[ $name == browser ]]
    then    
        list="http https chrome ftp javascript"
    else
        list="feed mailto news nntp snews"
    fi

    for prot in $list
    do
        gconftool-2 -t string -s $base/$prot/command "$param \"%s\""
    done

    exit
}

# run current

if [[ $name == browser ]] 
then
    $T exec $(getCmd http) $param
else
    $T exec $(getCmd mailto) $param
fi

^[1] Good luck!