[eschwartz]

Growing out of this discussion: Official Calibre PPA?, here is a simple bash script to update calibre on linux.
Note: This can also perform the first-time install, since the version check returns the same failure for out-of-date as it does if there is no calibre installed.

Thanks to aleyx for working on the version checking!

EDIT: The script has been updated to fix a few problems. Also, you can now install the script and add the systemd timer or cron job (defaults to systemd timer, falls back on cron) by running the following one-liner in a terminal:

sudo -v && wget -nv -O- https://github.com/eli-schwartz/calibre-installer/raw/master/linux/calibre-installer.sh | sudo bash -

Everything is managed through my GitHub repository

---

What this is doing, the manual way

---

New code:

Spoiler:

#!/bin/bash

# Unset git development source
export CALIBRE_DEVELOP_FROM=
# by default, switch is off
force_upgrade=0


# Functions

calibre_is_installed()
{
    command -v calibre >/dev/null 2>&1
}

usage()
{
	cat <<- _EOF_
		Usage: calibre-upgrade.sh [OPTIONS]
		Upgrades calibre installation. Automatically checks if the current version is up to date.
		Must be run as root.

		OPTIONS
		    -f, --force       Force an update. This is only useful if binaries
		                      were updated for a critical error. :shrug:
		    -h, --help        Displays this help message.
_EOF_
}

do_upgrade()
{
    if calibre_is_installed; then
        # shutdown calibre as each logged-in user.
        for i in $(users | tr ' ' '\n' | sort -u); do
            sudo -u $i calibre --shutdown-running-calibre
        done
        killall -q -v calibre-server && echo -e "Restart when upgrade is finished. ;)\n\n" || echo -e "No running calibre servers.\n\n"
    fi
    wget -nv -O- https://github.com/kovidgoyal/calibre/raw/master/setup/linux-installer.py | python -c "import sys; main=lambda x,y:sys.stderr.write('Download failed\n'); exec(sys.stdin.read()); main()"
}

# Options
while [ "$1" != "" ]; do
    case $1 in
        -h|--help)      usage
                        exit
                        ;;
        -f|--force)     shift
                        force_upgrade=1
                        ;;
        *)              echo "calibre-upgrade.sh: unrecognized option '$1'"
                        echo "Try 'calibre-upgrade.sh --help' for more information."
                        exit 1
    esac
    shift
done

# Main

## Check that we are running as root
if [[ $EUID -ne 0 ]]; then
    echo -e "You can only install calibre if you have root permission."
    exit 1
fi



if calibre_is_installed; then
    calibre-debug -c "import urllib as u; from calibre.constants import numeric_version; raise SystemExit(int(numeric_version  < (tuple(map(int, u.urlopen('http://code.calibre-ebook.com/latest').read().split('.'))))))"
    UP_TO_DATE=$?
else
    echo -e "Calibre is not installed, installing...\n\n"
    UP_TO_DATE=1
fi

if [ "$UP_TO_DATE" = 0 ]; then
    echo "Calibre is up-to-date"

    if [ "$force_upgrade" = 1 ]; then
        echo ""
        echo "Forcing upgrade anyway -- are you sure you want to continue? [y/n]"
        read answer

        if [[ "$answer" = "y" || "$answer" = "yes" ]]; then
            do_upgrade
        else
            echo "Exiting..."
            exit 1
        fi
    fi
else
    calibre_is_installed && echo -e "Calibre is out-of-date. Upgrading...\n\n"
    do_upgrade
fi

Old code:

Spoiler:

#!/bin/bash

calibre-debug -c "import urllib as u; from calibre.constants import numeric_version; raise SystemExit(int(numeric_version  < (tuple(map(int, u.urlopen('http://calibre-ebook.com/downloads/latest_version').read().split('.'))))))"

UP_TO_DATE=$?

if [ $UP_TO_DATE = 0 ]; then
	echo "Calibre is up-to-date"
else
	calibre --shutdown-running-calibre
	killall calibre-server

	sudo -v; wget -nv -O- https://github.com/kovidgoyal/calibre/raw/master/setup/linux-installer.py | sudo python -c "import sys; main=lambda:sys.stderr.write('Download failed\n'); exec(sys.stdin.read()); main()"
fi

Explanation:

Spoiler:

Very simply:

1. we start off with a one-liner which runs calibre-debug to determine the currently installed version, and compares it to the version declared at http://calibre-ebook.com/downloads/latest_version
2. if it returns negative, calibre is already up to date, and it tells you so. Why bother updating to the current version?
3. if not, we:
   
4. 1. close any running instances of calibre
   2. kill calibre-server, if running
   3. run Kovid's one-liner install code. If you use a non-default install directory, you can edit this!
      Just drop in Kovid's other code.

Save this as "calibre-upgrade.sh" (or whatever you want) and stick it in "/usr/bin/", to add it to your path. ("$HOME/bin/" works too, but this is for a system install, so this is nicer. )

You can now update calibre by running

sudo calibre-upgrade.sh

but to make this fully automatic, simply add:

0 6 * * 5 /usr/bin/calibre-upgrade.sh > /dev/null 2>&1

or if you want the output emailed to you by cron, add

0 6 * * 5 /usr/bin/calibre-upgrade.sh

to your crontab (with the command "sudo crontab -e") and the updater will run every Friday at 6:00 AM. Presumably, you aren't awake at that time, but you can fill in whatever time you want.

Attached is a zip of the updater script (in a bin directory, and marked as executable), which can be extracted to "/usr/" (or $HOME) for your convenience.