This script does is to add or remove the ssh keys of a github user to/from the authorized_keys file.

ssh_keys_manager.sh

#!/bin/bash

add_ssh_keys(){
github_username=$1
IFS=$'

'
# Iterate over all keys in the github account
for key in $(curl -sSL github.com/$github_username.keys)
do
    # Check if the key is already in the authorized_keys file
    if ! grep -q "$key" ~/.ssh/authorized_keys
    then
        # If not, add it
        echo "$key" >> ~/.ssh/authorized_keys
    fi
done
}

remove_ssh_keys(){
github_username=$1
IFS=$'

'
# Iterate over all keys in the authorized_keys file
for key in $(curl -sSL github.com/$github_username.keys)
do
    # add escape characters to the key
    key=$(echo "$key" | sed 's/\//\\\//g')
    # Check if the key is in the github account
    if grep $key ~/.ssh/authorized_keys
    then
        # If it is, remove it
        sed -i "/$key/d" ~/.ssh/authorized_keys
    fi
done
}

# Usage: manage_ssh_keys.sh [add|remove] [github_username]

if [ $# -ne 2 ]; then
    echo "Usage: $0 [add|remove] [github_username]"
    exit 1
fi

if [ "$1" == "add" ]; then
    add_ssh_keys $2
elif [ "$1" == "remove" ]; then
    remove_ssh_keys $2
else
    echo "Usage: $0 [add|remove] [github_username]"
    exit 1
fi