The last screen capture script you'll ever need.

screencapture

#!/bin/bash

TMP_NAME=$(mktemp -u ~/Downloads/capture.XXXXXX)

TMP_AVI="${TMP_NAME}.avi"
TMP_GIF="${TMP_NAME}.gif"
TMP_GIF_OPTIMIZED="${TMP_NAME}_optimized.gif"

print_usage()
{
  echo -e "Usage: screencapture [-t]\n\n\t-t seconds    capture time (default: 10)\n\t-o file    output file"
}

cleanup()
{
  rm -f $TMP_AVI
  rm -f $TMP_GIF
}

control_c()
# run if user hits control-c
{
  echo -en "\n*** Ouch! Exiting ***\n"
  cleanup
  exit $?
}

# trap keyboard interrupt (control-c)
trap control_c SIGINT


LENGTH=10

while getopts ":t:o:h" OPTION; do
  case "${OPTION}" in
    t)
      LENGTH=${OPTARG}
      ;;
    o)
      TMP_GIF_OPTIMIZED=${OPTARG}
      ;;
    h)
      print_usage
      exit 0
      ;;
    *) # echo "Incorrect options provided" exit 1 ;;
      echo "unknown option: $OPTION"
      exit 1
      ;;
  esac;
done

echo "Recording screen ($LENGTH seconds)"

ffcast -s lag 1 % ffmpeg -f x11grab -t $LENGTH -show_region 1 -framerate 20 -video_size %s -i %D+%c -codec:v huffyuv -vf crop="iw-mod(iw\\,2):ih-mod(ih\\,2)" $TMP_AVI

echo "Converting to GIF"
convert -quality 100% -layers Optimize $TMP_AVI $TMP_GIF

echo "Optimizing GIF"
gifsicle $TMP_GIF --colors 50 -l -O3 -o $TMP_GIF_OPTIMIZED

cleanup

echo "Wrote $TMP_GIF_OPTIMIZED"

BROWSER=chromium:firefox xdg-open "file://$(realpath $TMP_GIF_OPTIMIZED)"