Bash – pause youtube-dl when network is disconnected and resume when it is connected again

bashlinux-mintnetworkingprocess-managementshell-script

I am using Linux Mint 20.

I am using a vpn with a kill switch (protonvpn-cli ks --on).

So, if the vpn connection drops for some reason, the network get disconnected.

When the network get disconnected, my youtube-dl download stops permanently with the error

ERROR: Unable to download JSON metadata: <urlopen error [Errno -2] Name or service not known> (caused by URLError(gaierror(-2, 'Name or service not known')))

The issue is, I want youtube-dl to pause instead of closing, and resume when the connection is back.

I checked Retry when connection disconnect not working but I do not think it is relevant to my problem.

My config file looks like

--abort-on-error
--no-warnings
--console-title
--batch-file='batch-file.txt'
--socket-timeout 10
--retries 10
--continue
--fragment-retries 10

As I use batch files, I do not want to start the process from the beginning. I just want to pause the youtube-dl process till I get connected again and then continue the process.

How can I do that?

Update 1:

So far, what I have found is, to pause a process we can do something like:

$ kill -STOP 16143

To resume a process we can do something like:

$ kill -CONT 16143

I am not sure but think that we can know if my network is up or not by pinging1 2:

#!/bin/bash
HOSTS="cyberciti.biz theos.in router"

COUNT=4

for myHost in $HOSTS
do
  count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
  if [ $count -eq 0 ]; then
    # 100% failed 
    echo "Host : $myHost is down (ping failed) at $(date)"
  fi
done

However, it does not seem like an efficient solution.

Linux: execute a command when network connection is restored suggested using ifplugd or using /etc/network/if-up.d/.

There is another question and a blog post which mention using /etc/NetworkManager/dispatcher.d.

As I am using Linux Mint, I think any solution revolving around NetworkManager will be easier for me.

Best Answer

Here is something I wrote now that run on each line of batch-file.txt and run youtube-dl on it.
If there is no connection to the web site you trying to download from it will loop until connection restored (you should probably need to add some timeout on it since it will not stop.)
I used curl with expected 200 status code since if this don't work you probably won't be able to download.

The content of batch-file.txt is the same as before.

Running the script:

download.sh ./batch-file.txt {download_web_site_url}
# Example:
download.sh ./batch-file.txt google.com`

#!/bin/bash
# B"H

# Insted of using youtube-dl batch-file option read the file using bash.
URLS=$1 # "batch-file.txt"
# Pass the URL for site you trying to download from.
SITE_URL=$2

# This function check if url is returning 200 status code.
check_site_connection()
{
    # curl to 'your_site_url' with -I option for only the respons info only
    # pipe the respons tp awk with 'NR < 2' so only the first line with the status code is printed.
    # Return up if respons is 200.
    if [[ $(curl -Is $SITE_URL | awk 'NR < 2 {print $2}') == "200" ]];
    then
        echo up;
    else
        echo down;
    fi
}

# read the batch-file.
while IFS= read -r line
do
    # for each line in batch-file loop until conection to site is up with 2 seconds delay.
    while [[ $(check_site_connection) == "down" ]]
    do
        echo "waiting for internet conection"
        sleep 2
    done
    # run youtube-dl where line is the url to dowmload.
    ./youtube-dl "$line"
done < "$URLS"

Edit:

Just found this in the README.md and tested it working .
This for case each line is a playlist and not separate video.

youtube-dl --download-archive archive.txt URL_TO_PLAYLIST

This will download only new videos each time you run so if you add --download-archive archive.txt to the script above in ./youtube-dl --download-archive archive.txt "$line" So if it's start again it will go over all the playlist but will only start download from where it's stops.

Related Question