I have recently been trying to download an ISO of a certain Linux distro, but I find myself at the wrong end of a crappy connection. I tried downloading it with both Firefox and Chrome but both choked very early in the process, the current speed would go down to 0, and after a while the connection would just cutoff with no way to resume the download from where I left off.

Fear not because cURL comes to the rescue. After typing Up-Arrow and Enter more time than I care to admit, I decided to let the computer do the hard work and automate this whole thing. So I created a small Bash script called acurl.sh (for Automated cURL) that looks like this:

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export ec=1;

while [ $ec -gt 0 ];
do
    /usr/bin/curl -O -C - $1;
    export ec=$?;
done

if [ $ec -eq 0 ];
    echo "Downloaded $1";
fi

The code above expects you to pass the file to download as a parameter, which we have in the $1 variable. Then we tell curl to download it and write it to our local disk with the same name as the remote file (this is option -O). We also tell curl to resume a previous file download at a certain offset (this is done via option -C and giving it the value - will allow curl to automatically figure out how to resume the transfer). The next step is to capture curl error codes on exit. This is done by assigning the value of $? (which has the value of the most recent exit code) to our variable $ec. If $ec is greater than 0 then we try the download with curl again, otherwise we have a successful download.

Assuming that the script above is located somewhere in the $PATH, then using it is as simple as this:

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acurl.sh http://distrodomain.org/downloads/linux-distro-version-platform.iso

This is definitely a brute force approach, but it does the work.