Short and Painless

Listing 5 shows a function that sensibly splits up the download selection. You make the selection after listing the downloads by typing 1,2,3,4-10, for example. In this case, the script takes the downloads from 1 to 10, which are then sent to an array in the form of (1:*2 3:*4 ...).

function splitter () {
  sed 's/,/\n/g' <<<$* | sed -r '/-/ s/([0-9]+)-([0-9]+)/seq \1 \2/e' | sort -nu
}

The splitter function strips the string to remove the commas and creates a sorted, space-separated string of numbers from ranges such as 4-10. You can use these selection numbers later on to find the downloads contained in the indexed_downloads array.

Keep in mind that the count for Bash arrays always starts at  . For example, to select file number 5, you need to find it by querying indexed_indexes[4]. You can use the same index with the indexed_downloads array to retrieve the associated value.

Listing 6 shows the function that renames the files at download time. You need to pass in the base name of the URL as a parameter. At this point, the script is already in the right directory for the file extension (e.g., jpg/). The parameters starting in line 3 find other files that are already in the directory before the download starts. Bash uses the command from line 4 to check if there are files with the same name. If so, the script inserts an underscore (_) between the name and the dot that separates it from the file extension. This will also tell you how many times the file has been renamed. If the name contains one underscore, the file was renamed once; if it contains two, the file was renamed twice; and so on.

01 function rename () {
02   filename=$1
03   other_filenames=`echo ${@:2}`
04   while grep -q -F "${filename}" <<<${other_filenames}; do
05     filename=$(sed -r 's/(.+)(\.)(.+)/\1_\2\3/' <<<${filename})
06   done
07   echo ${filename}
08 }

At this point, you should debug the functions in detail by isolating them. For example, using sed and the command from Listing 7, you could write the warn and rename functions to a separate file, where you would then subsequently debug them with, for example,

bash -x debug

$ cat <(sed -r -n '/function (warn|rename)/,/^}/p' downloader_optimized2.bash) > debug

by renaming the function within the file and calling it with the associated parameters.

Listing 8 shows the download function, which first filters out the base name from the download link. To do this, it deletes all path information, as well as http://... or https://..., until only the actual file name remains. The script then finds the file extension and, if it does not already exist, creates a directory with this name. Then it changes to the directory and starts the download after running the rename function.

function download () {
  name=$(basename $1)
  suffix=$(cut -f 2 -d "." <<<${name})
  [ ! -e ${download_directory}/${suffix} ] && mkdir ${download_directory}/${suffix}
  cd ${download_directory}/${suffix} && files_in_directory=$(ls)
  future_name=$(rename $name $files_in_directory)
  wget -O $future_name $1
}

Listing 9 generates a menu that lists the available downloads. This function starts a loop that iterates across the indexed_downloads array and outputs the size and the base name from the array index one line at a time. At the end of the loop in line 6, everything is piped to gawk.

01 function menu () {
02   for index in ${!indexed_downloads[@]}; do
03     local base_name=$(basename ${indexed_downloads[$index]})
04     local size=${index}
05     echo "${size} ${base_name}"
06   done | gawk --assign free=${free} -F " " -f cutter.awk
07 }

Thanks to the -f cutter.awk option, gawk knows which AWK file to use as the program text. The call has an additional --assign free=${free} option, which ensures that the gawk script is aware of the free disk space previously determined in Bash. gawk then examines the file size and the base name one line at a time and evaluates both line by line.

Formatted Displays

The gawk script, cutter.awk, in Listing 10 starts with two functions I defined myself. The first function, cutter, truncates long basic names for the display by cutting them into two parts and dropping three dots into the middle. The second function, separating_line, generates separating lines in the display to improve clarity for download pages with a large number of links.

function cutter( word ){
  l = length(word)
  part1 = substr(word,1,8)
  part2 = substr(word,l-22)
  return part1"..."part2
}
function separating_line ( lesser_equal ) {
  for ( p = 0; p <= lesser_equal ; p++){
    printf "%s" (p == lesser_equal ? "\n" : "") ,"="
  }
}
BEGIN {
  i = 1
  printf "%8s %18s      %10s   %13s     %s\n", "Download", "Kilobytes", "Megabytes", "Gigabytes", "Filename"
  printf "%-5s %21.2f      %10.2f   %13.2f     %s\n", "Disc:", free, free/1024, free/(1024*1024),"home or /"
  separating_line(75)
}
{
  if ( length($2) > 40 ) {
    $2 = cutter($2)
  }
  printf "%2i => %21.2f   %13.2f   %13.2f     %s\n", i++, $1/1024, $1/(1024*1024), $1/(1024*1024*1024), $2
  total += $1
}
END {
  separating_line(75)
  printf "Totals: %19.2f   %13.2f   %13.2f     All downloads together\n", total/1024, total/(1024*1024), total/(1024*1024*1024)
}

The BEGIN block defines some basics as well as header formats. In addition, it shows the free space on the hard disk, or in your home directory, in the line following the header.

Finally, the command block without a pattern specification in lines 21 to 27 iterates through the individual lines, displaying the download size (in kilobytes, megabytes, and gigabytes) in the first field and the basic name in the second. This can be useful if you are downloading smaller files, such as wallpapers, ebooks, or MP3 files – output in gigabytes only, for example, would not make much sense here. This command block also computes the total size of all downloads and finally outputs it via the END block (Figure 1).

Figure 1: The formatted output shows the files provided by a website. To select a file, enter a number from the left.

Control

Finally, Listing 11 shows the main function that controls the entire program flow. As soon as you copy a URL from the browser by pressing Ctrl+C, xclip accesses it (line 1).

01 url=$(xclip -o 2>/dev/null)
02
03 if [ -z $url ]; then
04   warn "No URL present."
05   warn "Use [Ctrl]+[C] to copy the URL from the browser to the clipboard."
06   exit 1
07 fi
08
09 capture
10
11 if [ ${#download_links[@]} -gt 0 ]; then
12   menu
13   read -p "Select files (Example: 1,2,3-8,10 ): " selection
14 else
15   warn "NO DOWNLOADS PRESENT" && exit 1
16 fi
17
18 declare -i total_size_dowloads=0
19
20 for selection in $(splitter $selection); do
21   total_size_dowloads+=${indexed_indexes[((select - 1))]}
22   current_download=${indexed_downloads[${indexed_indexes[((select - 1))]}]}
23   if [[ ${frei}-5000 -lt ${total_size_dowloads}/1024 ]]; then
24     warn "Not enough free disc space."
25     warn "Canceling ${Current_download}."
26     exit 1
27   else
28     download $current_download
29   fi
30 done

If the graphical interface uses multiple clipboards (like FVWM), you need to use the -selection primary or secondary option to explicitly specify which clipboard xclip should use. After capturing the clipboard, the script checks whether the URL was also filled with the clipboard contents. If the URL has a length of zero, the program cancels the operation.

Lines 11 to 16 then check whether any download links have been captured on the page and whether they can be output. If there are no files to download, the script also terminates at this point.

Finally, a for loop processes all the downloads, checking their sizes and comparing them against the free disk space. If the size of the selected downloads exceeds the free disk space size, the script terminates.

Because all you need to do is copy the URL of the desired site for downloading files from the browser's address bar for the script to start automatically, this script works with all web browsers. The script retrieves the URL from the clipboard, evaluates the page for files that can be downloaded, and shows them to you sorted by size. You can then conveniently choose which of them you want to download.