基于python的修改hosts文件的脚本-internet.py

It works by modifying the /etc/hosts file. The hosts file associates numeric based addresses like 127.0.0.1 with named addresses like localhost. Usually this file is only used to cache local network names, as remote computers accessible over the internet have numeric addresses that may, and often do, change.
A web browser utilizes the Domain Name Service (DNS) to keep track of these dynamically changing numeric addresses. However before asking the remote DNS service for the numeric address of a domain like google.com, the computer will check the /etc/hosts file just in case the information is already there.
This means a web browser request for google.com can be redirected to a different numeric address of our choosing, instead of resolving to the actual address like 173.194.43.5.
By choosing an unused address, we can create a 'blackhole' where the requested site can not be reached. By default we use an address in the local 127.0.0.* range, but you can modify this to whatever you like in the settings below.
Note modern operating systems and web browsers cache DNS entries for a short time in order to cut down on the number of overall DNS calls. This DNS cache is checked before the /etc/hosts file. This script attempts to clear all local DNS caches. However you may need to clear a DNS cache manually, or simply wait a few minutes for the DNS cache to expire.
Note since this file modifies /etc/hosts, it will effect all users on the machine.
Why /etc/hosts? I'm not a big fan of cron requirements for scripts, but the alternative would be to pipe all traffic through a python daemon. I love Python, but unix based systems already do a good job networking without adding more cogs.
Why not /etc/resolve.conf? Mac OS X Darwin does not use /etc/resolve.conf in the same way Linux does. In the interests of this being cross-compatible I've decided to stick with /etc/hosts modification.

Usage - groups, domains, and times, oh my!

This script is meant to be flexible, allowing access depending on the time and day of the week.
Everything is organized into 'groups'. A group contains three pieces of information: a list of domains; a list of hours to be active during; a list of days to be active on.
Remember this script modifies the /etc/hosts file, which requires root privileges. Most command options require using sudo.

Groups

You can define as many groups as you want, or simply use the default group aptly named 'default.'

Examples

To add a new group: $ ./internet.py --add --group 'work'
Remove a group: $ ./internet.py --remove --group 'work'
Warning! This removes all information. See --activate/--deactivate below.

Active List

A group can be activated or deactivated. This allows you to create a group with set times and days, but temporarily turn the group off without deleting the hard work put into setting it up.
The 'default' group is active by default, and new groups are activated by default as well.

Examples

List current groups and their status $ ./internet.py --list
Deactivate a group: $ ./internet.py --deactivate --group 'work'
Activate a group: $ ./internet.py --activate --group 'work'

Domains

The core of this script is the list of domains to block. Domain names should not include 'http://' at the beginning. The 'http://' in a browser refers to the method, or protocol, the browser should use to connect to a domain. The domain name is the part that comes after it, e.g. google.com. This is the named address of the remote computer, and also the only part we care about.
Also, domains should not include any trailing information. For example write google.com, not google.com/ or google.com/analytics. Subdomains (information to the left) are okay, like translate.google.com.

Examples

Add a domain to the default group: $ ./internet.py --add --domain 'google.com'
Add a domain to a custom group: $ ./internet.py --add --domain 'google.com' --group 'work'
Empty all domains in a group: $ ./internet.py --empty domains --group 'work'
Notice This script only supports single arguments, e.g. one --domain, --hour or --day args. To add multiple domains, you must call internet.py multiple times.

Days

Days specify when a group's list of domains will be blocked. Days can be given by their full names (e.g. Monday), or as the wildcard '*'.
The default days range is '*', meaning it is active on all days. This is a valid range and can be added to any group.
Note adding the wildcard will overwrite current day ranges.

Examples

Add one day to a group: $ ./internet.py --add --day 'Tuesday'
Empty all days in a group: $ ./internet.py --empty days --group 'work'

Hours

Hours specify when a group's list of domains will be blocked. Hours can be given in single units (e.g. 8), in a range (e.g. 9-17), or as the wildcard '*'.
The default hours range is '*', meaning it is active all the time. This is a valid range and can be added to any group. Note adding the wildcard will overwrite current hour ranges.
All hours should be given as a 24 hour clock. Minutes are not supported and should not be used, e.g. write 9, not 9:00 or 900.

Examples

Add one hour to a group: $ ./internet.py --add --hour 8
Add an hour range to a group: $ ./internet.py --add --hour 9-17
Empty all hours in a group: $ ./internet.py --empty hours --group 'work'

Misc

There are more commands and functionality than outlined here. Run the help command (-h/--help) for a complete list of available flags/options.

Examples

List current groups and their status: `$ ./internet.py --list
View the hosts file before updating it: `$ ./internet.py --update --confirm
Print crontab information: `$ ./internet.py --print-crontab
Remember this script modifies the /etc/hosts file, which requires root privileges. Most command options require using sudo.

Recommendations

• Run the script hourly via a cron job. Use the --print-crontab option for help on how to set this up.
• Make sure this script has execute permissions (see $ man chmod for more information)
• Add internet.py to your PATH so it can be called/updated from any location on the command line.
• Alias internet.py to internet in your bashrc/zshrc. Alternatively remove the .py file extension (not recommended!)
• Don't use this script to limit other people's web browsing activities. It will do a poor job. The script is designed only to discourage casual browsing habits, not be a true gatekeeper.
• Read through the code before using it. It's short and well commented. Don't trust anyone's script that requires root privileges without looking it over yourself.
  
  from  https://github.com/chrislaskey/internet.py