Script for downloading free books from Springer

springer.sh

#!/bin/bash
#
# Usage:
# $ springer.sh
# will save all books
#
# $ springer.sh word
# will save all books whose titles or authors match "word"

# Link with books and links
springer="https://gist.githubusercontent.com/bishboria/8326b17bbd652f34566a/raw/0594f99c580c3befb924f3d36ab187c2da8f441b/springer-free-maths-books.md"

# Processing the argument
param=""
if [ ! -z "$1" ]
then
  export param="$1"
fi

while read -r book
do
  # Parsing markdown
  link=$(echo "$book" | awk -F'[][()]' '{print $4}')
  # Contains title and author
  naming=$(echo "$book" | awk -F'[][()]' '{print $2}')
  author=$(echo "$naming" | awk -F, '{print $NF}' | sed 's/^ //g')
  title=$(echo "$naming" | sed "s/$author$//" | rev | cut -c 3- | rev | sed 's/[:*"]//g')
  file="$title ($author).pdf"
  # If a file exists (that is, either the newest edition is already downloaded, or the script
  # is being run once again), then skip the book cuz we need neither older version nor duplicate
  if [ -f "$file" ]; then continue; fi
  # Downloading the file with a new name
  wget -O "$file" "$link" -q --show-progress -o /dev/null
# Get only lines that contain links, and output them in a reversed order
done < <(curl "$springer" | sed '/^[^[]*$/d' | sed '1!G;h;$!d' | grep -i "$param")

why it reports such error?
wget: unrecognized option '--show-progress'

@isaacmao
This option works for wget starting from version 1.16. Just update it.