byzanz-record-region

gistfile1.sh

#!/bin/bash

# Delay before starting
DELAY=10

# Sound notification to let one know when recording is about to start (and ends)
beep() {
    paplay /usr/share/sounds/KDE-Im-Irc-Event.ogg &
}

# Duration and output file
if [ $# -gt 0 ]; then
    D="--duration=$@"
else
    echo Default recording duration 10s to /tmp/recorded.gif
    D="--duration=10 /tmp/recorded.gif"
fi

# xrectsel from https://github.com/lolilolicon/FFcast2/blob/master/xrectsel.c
ARGUMENTS=$(xrectsel "--x=%x --y=%y --width=%w --height=%h") || exit -1

echo Delaying $DELAY seconds. After that, byzanz will start
for (( i=$DELAY; i>0; --i )) ; do
    echo $i
    sleep 1
done
beep
byzanz-record --verbose --delay=0 ${ARGUMENTS} $D
beep

I packaged xrectsel for Red Hat-based OS's on COPR: https://copr.fedorainfracloud.org/coprs/stbenjam/xrectsel/