Download edX Autonomous Mobile Robots (AMRx) Textbook to local.

amr_textbook.php

<?php
// Purpose: The edX AMR course textbook had extra large side buttons and very slow loading time, which was really annoying.
//          For personal use only.
// Note: Create a directory ./book before running PHP script.
// Example: 
//    mkdir ./book         # Create directory
//    sudo chmod +w./book  # Make the book directory writeable
//    vim amr_textbook.php # Copy paste the following script, save, exit (:wq)
//    php amr_textbook.php # Execute

$cnt = 1;
while($cnt < 474) {
   $num_page = sprintf("%03d", $cnt++);
   grab_image("https://s3.amazonaws.com/edx-textbooks/Siegwart--Autonomous+Mobile+Robots/p".$num_page.".png", "./book/p".$num_page.".png");
}
// Aggregate all PNGs to a single PDF
// sudo apt-get install imagemagick # If you don't have ImageMagick installed
exec("convert ./book/*.png Amr2ndEdition.pdf");

function grab_image($url,$saveto){
    $ch = curl_init ($url);
    curl_setopt($ch, CURLOPT_HEADER, 0); 
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
    curl_setopt($ch, CURLOPT_BINARYTRANSFER, 1); 
    $raw = curl_exec($ch);
    curl_close ($ch);
    if(file_exists($saveto)) unlink($saveto);
    $fp = fopen($saveto, 'x');
    fwrite($fp, $raw);
    fclose($fp);
}
?>