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@ -1,124 +0,0 @@
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[#]: collector: (lujun9972)
|
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[#]: translator: (chen-ni)
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||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
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[#]: subject: (How tracking pixels work)
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[#]: via: (https://jvns.ca/blog/how-tracking-pixels-work/)
|
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[#]: author: (Julia Evans https://jvns.ca/)
|
||||
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||||
How tracking pixels work
|
||||
======
|
||||
|
||||
I spent some time talking to a reporter yesterday about how advertisers track people on the internet. We had a really fun time looking at Firefox’s developer tools together (I’m not an internet privacy expert, but I do know how to use the network tab in developer tools!) and I learned a few things about how tracking pixels actually work in practice!
|
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|
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### the question: how does Facebook know that you went to Old Navy?
|
||||
|
||||
I often hear about this slightly creepy internet experience: you’re looking at a product online, and a day later see an ad for the same boots or whatever that you were looking at. This is called “retargeting”, but how does it actually work exactly in practice?
|
||||
|
||||
In this post we’ll experiment a bit and see exactly how Facebook can know what products you’ve looked at online! I’m using Facebook as an example in this blog post just because it’s easy to find websites with Facebook tracking pixels on them but of course almost every internet advertising company does this kind of tracking.
|
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|
||||
### the setup: allow third party trackers, turn off my adblocker
|
||||
|
||||
I use Firefox, and by default Firefox blocks a lot of this kind of tracking. So I needed to modify my Firefox privacy settings to get this tracking to work.
|
||||
|
||||
I changed my privacy settings from the default ([screenshot][1]) to a custom setting that allows third-party trackers ([screenshot][2]). I also disabled some privacy extensions I usually have running.
|
||||
|
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### tracking pixels: it’s not the gif, it’s the query parameters
|
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|
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A tracking pixel is a 1x1 gif that sites use to track you. By itself, obviously a tiny 1x1 gif doesn’t do too much. So how do tracking pixels track you? 2 ways:
|
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|
||||
1. Sites use the **query parameters** in the tracking pixel to add extra information like the URL of the page you’re visiting. So instead of just requesting `https://www.facebook.com/tr/` (which is a 44-byte 1x1 gif), it’ll request `https://www.facebook.com/tr/?the_website_you're_on`. (email marketers use similar tricks to figure out if you’ve opened an email, by giving the tracking pixel a unique URL)
|
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2. Sites send **cookies** with the tracking pixel so that they can tell that the person who visited oldnavy.com is the same as the person who’s using Facebook on the same computer.
|
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|
||||
|
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|
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### the Facebook tracking pixel on Old Navy’s website
|
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|
||||
To test this out, I went to look at a product on the Old Navy site with the URL [https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1][3] (a “Soft-Brushed Plaid Topcoat for Men”).
|
||||
|
||||
When I did that, the Javascript running on that page (presumably [this code][4]) sent a request to facebook.com that looks like this in Developer tools: (I censored most of the cookie values because some of them are my login cookies :) )
|
||||
|
||||
![][5]
|
||||
|
||||
Let’s break down what’s happening:
|
||||
|
||||
1. My browser sends a request to ` https://www.facebook.com/tr/?id=937725046402747&ev=PageView&dl=https%3A%2F%2Foldnavy.gap.com%2Fbrowse%2Fproduct.do%3Fpid%3D504753002%26cid%3D1125694%26pcid%3Dxxxxxx0%26vid%3D1%26grid%3Dpds_0_109_1%23pdp-page-content&rl=https%3A%2F%2Foldnavy.gap.com%2Fbrowse%2Fcategory.do%3Fcid%3D1135640%26mlink%3D5155%2Cm_mts_a&if=false&ts=1576684838096&sw=1920&sh=1080&v=2.9.15&r=stable&a=tmtealium&ec=0&o=30&fbp=fb.1.1576684798512.1946041422&it=15xxxxxxxxxx4&coo=false&rqm=GET`
|
||||
2. With that request, it sends a cookie called `fr` which is set to `10oGXEcKfGekg67iy.AWVdJq5MG3VLYaNjz4MTNRaU1zg.Bd-kxt.KU.F36.0.0.Bd-kx6.` (which I guess is my Facebook ad tracking ID)
|
||||
|
||||
|
||||
|
||||
So the three most notable things that are being sent in the tracking pixel query string are:
|
||||
|
||||
* the page I visited: [https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1#pdp-page-content][6]
|
||||
* the page that referred me to that page: [https://oldnavy.gap.com/browse/category.do?cid=1135640&mlink=5155,m_mts_a][7]
|
||||
* an identifier cookie for me: `10oGXEcKfGekg67iy.AWVdJq5MG3VLYaNjz4MTNRaU1zg.Bd-kxt.KU.F36.0.0.Bd-kx6.`
|
||||
|
||||
|
||||
|
||||
### now let’s visit Facebook!
|
||||
|
||||
Next, let’s visit Facebook, where I’m logged in. What cookies is my browser sending Facebook?
|
||||
|
||||
Unsurprisingly, it’s the same `fr` cookie from before: `10oGXEcKfGekg67iy.AWVdJq5MG3VLYaNjz4MTNRaU1zg.Bd-kxt.KU.F36.0.0.Bd-kx6.`. So Facebook now definitely knows that I (Julia Evans, the person with this Facebook account) visited the Old Navy website a couple of minutes ago and looked at a “Soft-Brushed Plaid Topcoat for Men”, because they can use that identifier to match up the data.
|
||||
|
||||
### these cookies are third-party cookies
|
||||
|
||||
The `fr` cookie that Facebook is using to track what websites I go to is called a “third party cookie”, because Old Navy’s website is using it to identify me to a third party (facebook.com). This is different from first-party cookies, which are used to keep you logged in.
|
||||
|
||||
Safari and Firefox both block many third-party cookies by default (which is why I had to change Firefox’s privacy settings to get this experiment to work), and as of today Chrome doesn’t (presumably because Chrome is owned by an ad company).
|
||||
|
||||
### sites have lots of tracking pixels
|
||||
|
||||
Like I expected, sites have **lots** of tracking pixels. For example, wrangler.com loaded 19 different tracking pixels in my browser from a bunch of different domains. The tracking pixels on wrangler.com came from: `ct.pinterest.com`, `af.monetate.net`, `csm.va.us.criteo.net`, `google-analytics.com`, `dpm.demdex.net`, `google.ca`, `a.tribalfusion.com`, `data.photorank.me`, `stats.g.doubleclick.net`, `vfcorp.dl.sc.omtrdc.net`, `ib.adnxs.com`, `idsync.rlcdn.com`, `p.brsrvr.com`, and `adservice.google.com`.
|
||||
|
||||
For most of these trackers, Firefox helpfully pointed out that it would have blocked them if I was using the standard Firefox privacy settings:
|
||||
|
||||
![][8]
|
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|
||||
### why browsers matter
|
||||
|
||||
The reason browsers matter so much is that your browser has the final word on what information it sends about you to which websites. The Javascript on the Old Navy’s website can ask your browser to send tracking information about you to Facebook, but your browser doesn’t have to do it! It can decide “oh yeah, I know that facebook.com/tr/ is a tracking pixel, I don’t want my users to be tracked, I’m just not going to send that request”.
|
||||
|
||||
And it can make that behaviour configurable by changing browser settings or installing browser extensions, which is why there are lots of privacy extensions.
|
||||
|
||||
### it’s fun to see how this works!
|
||||
|
||||
I think it’s fun to see how cookies / tracking pixels are used to track you in practice, even if it’s kinda creepy! I sort of knew how this worked before but I’d never actually looked at the cookies on a tracking pixel myself or what kind of information it was sending in its query parameters exactly.
|
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|
||||
And if you know how it works, it’s a easier to figure out how to be tracked less!
|
||||
|
||||
### what can you do?
|
||||
|
||||
I do a few small things to get tracked on the internet a little less:
|
||||
|
||||
* install an adblocker (like ublock origin or something), which will block a lot of tracker domains
|
||||
* use Firefox/Safari instead of Chrome (which have stronger default privacy settings right now)
|
||||
* use the [Facebook Container][9] Firefox extension, which takes extra steps to specifically prevent Facebook from tracking you
|
||||
|
||||
|
||||
|
||||
There are still lots of other ways to be tracked on the internet (especially when using mobile apps where you don’t have the same kind of control as with your browser), but I like understanding how this one method of tracking works and think it’s nice to be tracked a little bit less.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://jvns.ca/blog/how-tracking-pixels-work/
|
||||
|
||||
作者：[Julia Evans][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/chen-ni)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://jvns.ca/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://jvns.ca/images/trackers.png
|
||||
[2]: https://jvns.ca/images/firefox-insecure-settings.png
|
||||
[3]: https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1
|
||||
[4]: https://developers.facebook.com/docs/facebook-pixel/implementation/
|
||||
[5]: https://jvns.ca/images/fb-old-navy.png
|
||||
[6]: https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1#pdp-page-content
|
||||
[7]: https://oldnavy.gap.com/browse/category.do?cid=1135640&mlink=5155,m_mts_a
|
||||
[8]: https://jvns.ca/images/firefox-helpful.png
|
||||
[9]: https://addons.mozilla.org/en-CA/firefox/addon/facebook-container/
|
||||
@ -1,66 +0,0 @@
|
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[#]: collector: (lujun9972)
|
||||
[#]: translator: (HankChow)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Why your Python code needs to be beautiful and explicit)
|
||||
[#]: via: (https://opensource.com/article/19/12/zen-python-beauty-clarity)
|
||||
[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
|
||||
|
||||
Why your Python code needs to be beautiful and explicit
|
||||
======
|
||||
Welcome to Pythonukkah, a special series about the Zen of Python. On the
|
||||
first day, we celebrate the first two principles: beauty and
|
||||
explicitness.
|
||||
![Searching for code][1]
|
||||
|
||||
Python contributor Tim Peters introduced us to the [Zen of Python][2] in 1999. Twenty years later, its 19 guiding principles continue to be relevant within the community. We start our Pythonukkah celebration—like Hanukkah, a festival of lights—with the first two principles in the Zen of Python: on beauty and explicitness.
|
||||
|
||||
> "Hanukkah is the Festival of Lights,
|
||||
> Instead of one day of presents, we get eight crazy nights."
|
||||
> —Adam Sandler, [_The Hanukkah Song_][3]
|
||||
|
||||
### Beautiful is better than ugly.
|
||||
|
||||
It was in _[Structure and Interpretation of Computer Programs][4]_ (_SICP_) that the point was made: "Programs must be written for people to read and only incidentally for machines to execute." Machines do not care about beauty, but people do.
|
||||
|
||||
A beautiful program is one that is enjoyable to read. This means first that it is consistent. Tools like [Black][5], [flake8][6], and [Pylint][7] are great for making sure things are reasonable on a surface layer.
|
||||
|
||||
But even more important, only humans can judge what humans find beautiful. Code reviews and a collaborative approach to writing code are the only realistic way to build beautiful code. Listening to other people is an important skill in software development.
|
||||
|
||||
Finally, all the tools and processes are moot if the _will_ is not there. Without an appreciation for the importance of beauty, there will never be an emphasis on writing beautiful code.
|
||||
|
||||
This is why this is the first principle: it is a way of making "beauty" a value in the Python community. It immediately answers: "Do we _really_ care about beauty?" We do.
|
||||
|
||||
### Explicit is better than implicit.
|
||||
|
||||
We humans celebrate light and fear the dark. Light helps us make sense of vague images. In the same way, programming with more explicitness helps us make sense of abstract ideas. It is often tempting to make things implicit.
|
||||
|
||||
"Why is **self** explicitly there as the first parameter of methods?"
|
||||
|
||||
There are many technical explanations, but all of them are wrong. It is almost a Python programmer's rite of passage to write a metaclass that makes explicitly listing **self** unnecessary. (If you have never done this before, do so; it makes a great metaclass learning exercise!)
|
||||
|
||||
The reason **self** is explicit is not because the Python core developers did not want to make a metaclass like that the "default" metaclass. The reason it is explicit is because there is one less special case to teach: the first argument is _explicit_.
|
||||
|
||||
Even when Python does allow non-explicit things, such as context variables, we must always ask: Are we sure we need them? Could we not just pass arguments explicitly? Sometimes, for many reasons, this is not feasible. But prioritizing explicitness means, at the least, asking the question and estimating the effort.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/12/zen-python-beauty-clarity
|
||||
|
||||
作者：[Moshe Zadka][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://opensource.com/users/moshez
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/search_find_code_python_programming.png?itok=ynSL8XRV (Searching for code)
|
||||
[2]: https://www.python.org/dev/peps/pep-0020/
|
||||
[3]: https://en.wikipedia.org/wiki/The_Chanukah_Song
|
||||
[4]: https://en.wikipedia.org/wiki/Structure_and_Interpretation_of_Computer_Programs
|
||||
[5]: https://opensource.com/article/19/5/python-black
|
||||
[6]: https://opensource.com/article/19/5/python-flake8
|
||||
[7]: https://opensource.com/article/19/10/python-pylint-introduction
|
||||
@ -1,119 +0,0 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Unix is turning 50. What does that mean?)
|
||||
[#]: via: (https://www.networkworld.com/article/3511428/unix-is-turning-50-what-does-that-mean.html)
|
||||
[#]: author: (Sandra Henry-Stocker https://www.networkworld.com/author/Sandra-Henry_Stocker/)
|
||||
|
||||
Unix is turning 50. What does that mean?
|
||||
======
|
||||
Unix time, also known as 'epoch time,' is the number of seconds that have passed since Jan 1, 1970. As Unix turns 50, let's take a look at what worries kernel developers.
|
||||
[cbaquiran][1] [(CC0)][2]
|
||||
|
||||
2020 is a significant year for Unix. At the very start of the year, Unix turns 50.
|
||||
|
||||
While some of the early development of Unix predates the official start of its "epoch," Jan 1, 1970 remains the zero-point in POSIX time and the recognized beginning of all things Unix. Jan 1, 2020 will mark 50 years since that moment.
|
||||
|
||||
### Unix time vs human time
|
||||
|
||||
In terms of human time, 50 years is a big deal. In terms of Unix time, there's nothing particularly special about 50 years. 48.7 years would be no less significant.
|
||||
|
||||
[][3]
|
||||
|
||||
BrandPost Sponsored by HPE
|
||||
|
||||
[Take the Intelligent Route with Consumption-Based Storage][3]
|
||||
|
||||
Combine the agility and economics of HPE storage with HPE GreenLake and run your IT department with efficiency.
|
||||
|
||||
Unix (including Linux) systems store date/time values as the number of seconds that have elapsed since 1970-01-01 00:00:00 UTC in 32 bits. To determine how many seconds have passed since that time and, thus, what right now looks like as a Unix time value, you can issue a command like this:
|
||||
|
||||
```
|
||||
$ date +%s
|
||||
1576883876
|
||||
```
|
||||
|
||||
The **%s** argument tells the date command to display the current date/time as the number of seconds since the start of 1970-01-01.
|
||||
|
||||
### How much time can Unix systems manage?
|
||||
|
||||
To understand how much time Unix systems can accommodate, we need to look at the capacity of a 32-bit field. It can be calculated like this:
|
||||
|
||||
```
|
||||
$ echo '2^32' | bc
|
||||
4294967296
|
||||
```
|
||||
|
||||
However, since Unix needs to accommodate negative numbers, it reserves one bit for a number's sign, thus reducing this to:
|
||||
|
||||
```
|
||||
$ echo '2^31' | bc
|
||||
2147483648
|
||||
```
|
||||
|
||||
And, since Unix numbering begins with 0, that means we have 2,147,483,648 values, but the largest possible value is 2,147,483,647. Unix date/time values cannot exceed that number – just like the odometer on your car probably can't exceed 999,999 miles. Add 1 and the value turns to 0.
|
||||
|
||||
### How long is a year in seconds?
|
||||
|
||||
The number of seconds in most years can be calculated like this – hours/day multiplied by minutes/hour multiplied by seconds/minute multiplied by the number of days in a year:
|
||||
|
||||
```
|
||||
$ expr 24 \* 60 \* 60 \* 365
|
||||
31536000
|
||||
```
|
||||
|
||||
In leap years, we just add another day:
|
||||
|
||||
```
|
||||
$ expr 24 \* 60 \* 60 \* 366
|
||||
31622400
|
||||
```
|
||||
|
||||
### **How will Unix see its 50 year birthday?**
|
||||
|
||||
12:00 AM on Jan 1, 2020 will be **1577836800** in epoch time. The calculation is a little tricky, but mostly because we have to accommodate leap years. Since the start of the epoch, we've had 12 leap years, starting in 1972, the last in 2016. And, when we reach 2020, we will have had 38 regular years.
|
||||
|
||||
Here’s a calculation using the **expr** command to count the seconds in these 50 years:
|
||||
|
||||
```
|
||||
$ expr 24 \* 60 \* 60 \* 365 \* 38 + 24 \* 60 \* 60 \* 366 \* 12
|
||||
1577836800
|
||||
```
|
||||
|
||||
The first half of that is calculating the seconds in the 38 non-leap years. We then add a similar calculation for leap years with their 366 days. Conversely, you could use the seconds per year figures presented earlier and just do this:
|
||||
|
||||
```
|
||||
$ expr 31536000 \* 38 + 31622400 \* 12
|
||||
1577836800
|
||||
```
|
||||
|
||||
This way of tracking dates and times made Unix systems fairly impervious to the Y2K scare that had people in late 1999 worried that moving into the year 2000 would wreak havoc on computer systems. Far fewer problems were experienced than people feared. In fact, only applications which stored years in a two-digit format would see the year going to 00 as a sign that time jumping backwards. Still, lots of application developers had some tedious extra work piled onto their plates to ensure that their systems wouldn’t run into serious problems when 2000 hit.
|
||||
|
||||
### When Unix time will run into problems
|
||||
|
||||
Unix systems won’t run into a **Y2K** type of problem until **2038** when dates stored as described above will overrun their 32-bit space allotments. But that’s 18 years from now, and kernel developers are already working on how they will avert disaster. It’s a bit too early to start panicking.
|
||||
|
||||
The year 2038 problem is sometimes referred to as the **Y2K38** problem. We have until Tuesday, January 19, 2038 to address it. If the problem isn’t resolved, systems after that date may think it’s 1901. One way to address the problem would be to switch to 64-bit representations of date/time information. Some people believe that even that will be a lot more complex than it sounds. In any case, it’s probably still too early to panic. And, in the meantime, maybe after singing "Auld Lang Syne" this New Year’s Eve, you can sing "Happy Birthday" to Unix. It’s turning 50, and that’s still a very big deal.
|
||||
|
||||
Join the Network World communities on [Facebook][4] and [LinkedIn][5] to comment on topics that are top of mind.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.networkworld.com/article/3511428/unix-is-turning-50-what-does-that-mean.html
|
||||
|
||||
作者：[Sandra Henry-Stocker][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://www.networkworld.com/author/Sandra-Henry_Stocker/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://pixabay.com/en/birthday-cake-cake-birthday-380178/
|
||||
[2]: https://creativecommons.org/publicdomain/zero/1.0/
|
||||
[3]: https://www.networkworld.com/article/3440100/take-the-intelligent-route-with-consumption-based-storage.html?utm_source=IDG&utm_medium=promotions&utm_campaign=HPE20773&utm_content=sidebar ( Take the Intelligent Route with Consumption-Based Storage)
|
||||
[4]: https://www.facebook.com/NetworkWorld/
|
||||
[5]: https://www.linkedin.com/company/network-world
|
||||
116
translated/tech/20191218 How tracking pixels work.md
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[#]: collector: (lujun9972)
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[#]: translator: (chen-ni)
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[#]: reviewer: ( )
|
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[#]: publisher: ( )
|
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[#]: url: ( )
|
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[#]: subject: (How tracking pixels work)
|
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[#]: via: (https://jvns.ca/blog/how-tracking-pixels-work/)
|
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[#]: author: (Julia Evans https://jvns.ca/)
|
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|
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追踪像素是如何工作的？
|
||||
======
|
||||
|
||||
昨天，我和一名记者谈到了一个问题：广告商是如何在互联网上对人们进行追踪的？我们津津有味地查看了 Firefox 的开发者工具（虽然我不是一个互联网隐私专家，但至少还会使用开发者工具中的“network”标签页），从中我终于弄明白追踪像素在实际中是如何工作的了。
|
||||
|
||||
### 问题：Facebook 怎么知道你逛了 Old Navy？
|
||||
|
||||
我时常听人们说起这种有些诡异的上网经历：你在线上浏览了一个商品，一天之后，竟然看到了同一款靴子（或者是别的什么你当时浏览的商品）的广告。这就是所谓的“再营销”，但它到底是如何实现的呢？
|
||||
|
||||
在本文中，我们来进行一个小实验，看看 Facebook 究竟是怎么知道你在线上浏览了什么商品的。这里使用 Facebook 作为示例，只是因为很容易找到投放了 Facebook 追踪像素的网站；其实，几乎所有互联网广告公司都会使用类似的追踪技术。
|
||||
|
||||
### 准备：允许第三方追踪器，同时关闭广告拦截器
|
||||
|
||||
我使用的浏览器是 Firefox，但是 Firefox 默认拦截了很多这种类型的追踪，所以需要修改 Firefox 的隐私设置，才能让这种追踪生效。
|
||||
|
||||
首先，我将隐私设置从默认设置（[截图][1]）修改为允许第三方追踪器的个性化设置（[截图][2]），然后禁用了一些平时运行的隐私保护扩展。
|
||||
|
||||
### 追踪像素：关键不在于 gif，而在于请求参数
|
||||
|
||||
追踪像素是网站用来追踪你的一个 1x1 大小的 gif。就其本身而言，一个小小的 1x1 gif 显然起不到什么作用。那么，追踪像素到底是如何进行追踪的？其中涉及两个方面：
|
||||
|
||||
1. 通过使用追踪像素上的**请求参数**，网站可以添加额外的信息，比如你正在访问的页面。这样一来，请求的就不是 `https://www.facebook.com/tr/`（这个链接是一个 44 字节大小的 1x1 gif），而是 `https://www.facebook.com/tr/?the_website_you're_on`。（邮件营销人员会使用类似的技巧，通过为追踪像素指定一个独特的 URL，弄清楚你是否打开了某一封邮件。）
|
||||
2. 在发送该请求的同时，还发送了相应的 cookie。这样一来广告商就可以知道，访问 oldnavy.com 的这个人和在同一台电脑上使用 Facebook 的是同一个人。
|
||||
|
||||
### Old Navy 网站上的 Facebook 追踪像素
|
||||
|
||||
为了对此进行验证，我在 Old Navy（GAP 旗下的一个服装品牌）网站上浏览了一个商品，相应的URL是 [https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1][3]（这是一件“男款短绒格子花呢大衣”）。
|
||||
|
||||
在我浏览这个商品的同时，页面上运行的 Javascript（用的应该是[这段代码][4]）向 facebook.com 发送了一个请求。在开发者工具中，该请求看上去是这样的：（我屏蔽了大部分 cookie 值，因为其中有一些是我的登录 cookie）
|
||||
|
||||
![][5]
|
||||
|
||||
下面对其进行拆解分析：
|
||||
|
||||
1. 我的浏览器向 ` https://www.facebook.com/tr/?id=937725046402747&ev=PageView&dl=https%3A%2F%2Foldnavy.gap.com%2Fbrowse%2Fproduct.do%3Fpid%3D504753002%26cid%3D1125694%26pcid%3Dxxxxxx0%26vid%3D1%26grid%3Dpds_0_109_1%23pdp-page-content&rl=https%3A%2F%2Foldnavy.gap.com%2Fbrowse%2Fcategory.do%3Fcid%3D1135640%26mlink%3D5155%2Cm_mts_a&if=false&ts=1576684838096&sw=1920&sh=1080&v=2.9.15&r=stable&a=tmtealium&ec=0&o=30&fbp=fb.1.1576684798512.1946041422&it=15xxxxxxxxxx4&coo=false&rqm=GET` 发送了一个请求；
|
||||
2. 与该请求同时发送的，还有一个名为 `fr` 的 cookie，取值为 `10oGXEcKfGekg67iy.AWVdJq5MG3VLYaNjz4MTNRaU1zg.Bd-kxt.KU.F36.0.0.Bd-kx6.`（估计是我的 Facebook 广告追踪 ID）
|
||||
|
||||
在所发送的追踪像素查询字符串里，有三个值得注意的地方：
|
||||
|
||||
* 我当前访问的页面：[https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1#pdp-page-content][6]
|
||||
* 引导我来到当前页面的上一级页面：[https://oldnavy.gap.com/browse/category.do?cid=1135640&mlink=5155,m_mts_a][7]；
|
||||
* 作为我的身份标识的 cookie：`10oGXEcKfGekg67iy.AWVdJq5MG3VLYaNjz4MTNRaU1zg.Bd-kxt.KU.F36.0.0.Bd-kx6.`
|
||||
|
||||
### 下面来逛逛 Facebook！
|
||||
|
||||
下面来逛逛 Facebook 吧。我之前已经登入了 Facebook，猜猜看，我的浏览器发送给 Facebook 的 cookie 是什么？
|
||||
|
||||
不出所料，正是之前见过的 `fr` cookie：`10oGXEcKfGekg67iy.AWVdJq5MG3VLYaNjz4MTNRaU1zg.Bd-kxt.KU.F36.0.0.Bd-kx6.`。Facebook 现在一定知道我（Julia Evans，这个 Facebook 账号所关联的人）在几分钟之前访问了 Old Navy 网站，并且浏览了“男款短绒格子花呢大衣”，因为他们可以使用这个 cookie 将数据串联起来。
|
||||
|
||||
### 这里涉及到的是第三方 cookie
|
||||
|
||||
Facebook 用来追踪我访问了哪些网站的 cookie，属于所谓的“第三方 cookie”，因为 Old Navy 的网站使用它为一个第三方（即 facebook.com）确认我的身份。这和用来维持登录状态的“第一方 cookie”有所不同。
|
||||
|
||||
Safari 和 Firefox 默认都会拦截许多第三方 cookie（所以需要更改 Firefox 的隐私设置，才能够进行这个实验），而 Chrome 目前并不进行拦截（很可能是因为 Chrome 的所有者正是一个广告公司）。
|
||||
|
||||
### 网站上的追踪像素有很多
|
||||
|
||||
如我所料，网站上的追踪像素有 **很多**。比如，wrangler.com 在我的浏览器里加载了来自不同域的 19 个不同的追踪像素。wrangler.com 上的追踪像素分别来自：`ct.pinterest.com`、`af.monetate.net`、`csm.va.us.criteo.net`、`google-analytics.com`、`dpm.demdex.net`、`google.ca`、`a.tribalfusion.com`、`data.photorank.me`、`stats.g.doubleclick.net`、`vfcorp.dl.sc.omtrdc.net`、`ib.adnxs.com`、`idsync.rlcdn.com`、`p.brsrvr.com`，以及`adservice.google.com`。
|
||||
|
||||
Firefox 贴心地指出，如果使用 Firefox 的标准隐私设置，其中的大部分追踪器都会被拦截：
|
||||
|
||||
![][8]
|
||||
|
||||
### 浏览器的重要性
|
||||
|
||||
浏览器之所以如此重要，是因为你的浏览器最终决定了发送你的什么信息、发送到哪些网站。Old Navy 网站上的 Javascript 可以请求你的浏览器向 Facebook 发送关于你的追踪信息，但浏览器可以拒绝执行。浏览器的决定可以是：“哈，我知道 facebook.com/tr/ 是一个追踪像素，我不想让我的用户被追踪，所以我不会发送这个请求”。
|
||||
|
||||
浏览器还可以允许用户对上述行为进行配置，方法包括更改浏览器设置，以及安装浏览器扩展（所以才会有如此多的隐私保护扩展）。
|
||||
|
||||
### 摸清其中原理，实为一件趣事
|
||||
|
||||
在我看来，弄清楚 cookie / 追踪像素是怎么用于对你进行追踪的，实在是一件趣事（尽管显得有点阴险）。我之前大概明白其中的道理，但是并没有亲自查看过追踪像素上的 cookie，也没有看过发送的查询参数上究竟包含什么样的信息。
|
||||
|
||||
当然，明白了其中的原理，也就更容易降低被追踪的概率了。
|
||||
|
||||
### 可以采取的措施
|
||||
|
||||
为了尽量避免在互联网上被追踪，我采取了几种简单的措施:
|
||||
|
||||
* 安装一个广告拦截器（比如 ublock origin 之类）。广告拦截器可以针对许多追踪器的域进行拦截。
|
||||
* 使用目前默认隐私保护强度更高的 Firefox/Safari，而不是 Chrome。
|
||||
* 使用 [Facebook Container][9] 这个 Firefox 扩展。该扩展针对 Facebook 进一步采取了防止追踪的措施。
|
||||
|
||||
虽然在互联网上被追踪的方式还有很多（尤其是在使用手机应用的时候，因为在这种情况下，你没有和像对浏览器一样的控制程度），但是能够理解这种追踪方法的工作原理，稍微减少一些被追踪的可能性，也总归是一件好事。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://jvns.ca/blog/how-tracking-pixels-work/
|
||||
|
||||
作者：[Julia Evans][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/chen-ni)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://jvns.ca/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://jvns.ca/images/trackers.png
|
||||
[2]: https://jvns.ca/images/firefox-insecure-settings.png
|
||||
[3]: https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1
|
||||
[4]: https://developers.facebook.com/docs/facebook-pixel/implementation/
|
||||
[5]: https://jvns.ca/images/fb-old-navy.png
|
||||
[6]: https://oldnavy.gap.com/browse/product.do?pid=504753002&cid=1125694&pcid=1135640&vid=1&grid=pds_0_109_1#pdp-page-content
|
||||
[7]: https://oldnavy.gap.com/browse/category.do?cid=1135640&mlink=5155,m_mts_a
|
||||
[8]: https://jvns.ca/images/firefox-helpful.png
|
||||
[9]: https://addons.mozilla.org/en-CA/firefox/addon/facebook-container/
|
||||
@ -0,0 +1,65 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (HankChow)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Why your Python code needs to be beautiful and explicit)
|
||||
[#]: via: (https://opensource.com/article/19/12/zen-python-beauty-clarity)
|
||||
[#]: author: (Moshe Zadka https://opensource.com/users/moshez)
|
||||
|
||||
为什么 Python 代码要写得美观而明确
|
||||
======
|
||||
欢迎阅读“Python 光明节（Pythonukkah）”系列文章，这个系列文章将会讨论《Python 之禅》。我们首先来看《Python 之禅》里的前两个原则：美观与明确。
|
||||
![Searching for code][1]
|
||||
|
||||
早在 1999 年，Python 的贡献者之一，Tim Peters 就提出了《[Python 之禅][2]》，直到二十年后的今天，《Python 之禅》中的 19 条原则仍然对整个社区都产生着深远的影响。为此，我们举行了这一次的“Python 光明节”。首先，我们会讨论《Python 之禅》中的前两个原则：美观和明确。
|
||||
|
||||
> "Hanukkah is the Festival of Lights,
|
||||
> Instead of one day of presents, we get eight crazy nights."
|
||||
> —亚当·桑德勒, [光明节之歌][3]
|
||||
|
||||
### 美观胜于丑陋
|
||||
|
||||
著名的《[<ruby>计算机程序的构造和解释<rt>Structure and Interpretation of Computer Programs</rt></ruby>][4]》中有这么一句话：代码是写给人看的，只是恰好能让机器运行（Programs must be written for people to read and only incidentally for machines to execute.）。毕竟机器并不在乎代码的美观性，但人类在乎。
|
||||
|
||||
阅读美观的代码对人们来说是一种享受，这就要求在整套代码中保持一致的风格。使用诸如 [Black][5]、[flake8][6]、[Pylint][7] 这一类工具能够有效地接近这一个目标。
|
||||
|
||||
但实际上，只有人类自己才知道什么才是真正的美观。因此，代码审查和协同开发是其中的不二法门，同时，在开发过程中倾听别人的意见也是必不可少的。
|
||||
|
||||
最后，个人的主观能动性也很重要，否则一切工具和流程都会变得毫无意义。只有意识到美观的重要性，才能主动编写出美观的代码。
|
||||
|
||||
这就是为什么美观在众多原则当中排到了首位，它让“美”成为了 Python 社区的一种价值。如果有人要问，”我们真的在乎美吗？“社区会以代码给出肯定的答案。
|
||||
|
||||
### 明确胜于隐晦
|
||||
|
||||
人类会欢庆光明、惧怕黑暗，那是因为光能够让我们看到难以看清的事物。同样地，尽管有些时候我们会不自觉地把代码写得含糊不清，但明确地编写代码确实能够让我们理解很多抽象的概念。
|
||||
|
||||
“为什么类方法中要将 `self` 显式指定为第一个参数？”
|
||||
|
||||
这个问题已经是老生常谈了，但网络上很多流传已久的回答都是不准确的。在编写<ruby>元类<rt>metaclass</rt></ruby>时，显式指定 `self` 参数就显得毫无意义。如果你没有编写过元类，希望你可以尝试一下，这是很多 Python 程序员的必经之路。
|
||||
|
||||
显式指定 `self` 参数的原因并不是 Python 的设计者不想将这样的元类视为“默认”元类，而是因为第一个参数必须是显式的。
|
||||
|
||||
即使 Python 中确实允许非显式的情况存在（例如上下文变量），但我们还是应该提出疑问：某个东西是不是有存在的必要呢？如果非显式地传递参数会不会出现问题呢？有些时候，由于种种原因，这是会有问题的。总之，在写代码时一旦能够优先考虑到明确性，至少意味着能对不明确的地方提出疑问并对结果作出有效的估计。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/12/zen-python-beauty-clarity
|
||||
|
||||
作者：[Moshe Zadka][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[HankChow](https://github.com/HankChow)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://opensource.com/users/moshez
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/search_find_code_python_programming.png?itok=ynSL8XRV "Searching for code"
|
||||
[2]: https://www.python.org/dev/peps/pep-0020/
|
||||
[3]: https://en.wikipedia.org/wiki/The_Chanukah_Song
|
||||
[4]: https://en.wikipedia.org/wiki/Structure_and_Interpretation_of_Computer_Programs
|
||||
[5]: https://opensource.com/article/19/5/python-black
|
||||
[6]: https://opensource.com/article/19/5/python-flake8
|
||||
[7]: https://opensource.com/article/19/10/python-pylint-introduction
|
||||
|
||||
@ -0,0 +1,111 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (wxy)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Unix is turning 50. What does that mean?)
|
||||
[#]: via: (https://www.networkworld.com/article/3511428/unix-is-turning-50-what-does-that-mean.html)
|
||||
[#]: author: (Sandra Henry-Stocker https://www.networkworld.com/author/Sandra-Henry_Stocker/)
|
||||
|
||||
Unix 即将迎来 50 岁
|
||||
======
|
||||
|
||||
Unix 时间（又称为“<ruby>纪元时间<rt>epoch time</rt></ruby>”）是自 1970 年 1 月 1 日以来经过的秒数。当 Unix 即将 50 岁时，让我们看一下让内核开发人员担心的地方。
|
||||
|
||||
[cbaquiran][1]
|
||||
|
||||
对于 Unix 而言，2020 年是重要的一年。在这一年年初，Unix 进入 50 岁。
|
||||
|
||||
尽管 Unix 的某些早期开发早于其“纪元”的正式开始，但 1970 年 1 月 1 日仍然是 POSIX 时间的零点，也是公认的 Unix 的万物之始。自那一刻算起，2020 年 1 月 1 日将是其 50 周年。
|
||||
|
||||
### Unix 时间与人类时间
|
||||
|
||||
就人类时间而言，50 年是很重要的。就 Unix 时间而言，50 年没有什么特别的。48.7 年同样重要。
|
||||
|
||||
Unix（包括 Linux）系统将日期/时间值存储为自 1970-01-01 00:00:00 UTC 以来经过的秒数（32 位二进制）。要确定自该时间以来经过了几秒钟，看看 Unix 时间值是什么样子，你可以发出如下命令：
|
||||
|
||||
```
|
||||
$ date +%s
|
||||
1576883876
|
||||
```
|
||||
|
||||
`％s` 参数告诉 `date` 命令将当前日期/时间显示为自 1970-01-01 开始以来的秒数。
|
||||
|
||||
### Unix 系统可以管理多少时间？
|
||||
|
||||
要了解 Unix 系统可以容纳多少时间，我们需要查看 32 位字段的容量。可以这样计算：
|
||||
|
||||
```
|
||||
$ echo '2^32' | bc
|
||||
4294967296
|
||||
```
|
||||
|
||||
但是，由于 Unix 需要容纳负数，因此它会为数字的符号保留一位，从而将其减少为：
|
||||
|
||||
```
|
||||
$ echo '2^31' | bc
|
||||
2147483648
|
||||
```
|
||||
|
||||
并且，由于 Unix 计数以 0 开头，这意味着我们有 2,147,483,648 个值，但最大的可能值为 2,147,483,647 个。Unix 日期/时间值不能超过该数字——就像汽车上的里程表可能不能超过 999,999 英里一样。加 1 该值就变为了 -2147483648。（LCTT 译注：此处原文描述有误，已修改。在达到最大值之后，即 2018/1/19 03:14:07，下 1 秒导致符号位变为 1，其余 31 位为 0，即 -2147483648，时间变为 1901/12/13 20:45:52，这就是 Y2K38 问题。）
|
||||
|
||||
### 一年有多少秒？
|
||||
|
||||
大多数年份的秒数可以这样计算：每天的小时数乘以每小时的分钟数乘以每分钟的秒数乘以一年中的天数：
|
||||
|
||||
```
|
||||
$ expr 24 \* 60 \* 60 \* 365
|
||||
31536000
|
||||
```
|
||||
|
||||
在闰年，我们再增加一天：
|
||||
|
||||
```
|
||||
$ expr 24 \* 60 \* 60 \* 366
|
||||
31622400
|
||||
```
|
||||
|
||||
### Unix 将如何庆祝其 50 岁生日？
|
||||
|
||||
2020 年 1 月 1 日中午 12:00 是纪元时间的 1577836800。这个计算有些棘手，但主要是因为我们必须适应闰年。自该纪元开始以来，我们经历了 12 个闰年，从 1972 年开始，到上一个闰年是 2016 年。而且，当我们达到 2020 年时，我们将有 38 个常规年份。
|
||||
|
||||
这是使用 `expr` 命令进行的计算，以计算这 50 年的秒数：
|
||||
|
||||
```
|
||||
$ expr 24 \* 60 \* 60 \* 365 \* 38 + 24 \* 60 \* 60 \* 366 \* 12
|
||||
1577836800
|
||||
```
|
||||
|
||||
前半部分是计算 38 个非闰年的秒数。然后，我们加上闰年的 366 天的类似计算。或者，你可以使用前面介绍的每年秒数，然后执行以下操作：
|
||||
|
||||
```
|
||||
$ expr 31536000 \* 38 + 31622400 \* 12
|
||||
1577836800
|
||||
```
|
||||
|
||||
这种跟踪日期和时间的方式使 Unix 系统完全不受 Y2K 恐慌的影响，1999 年末人们开始担心进入 2000 年会对计算机系统造成严重破坏。但是实际遇到的问题比人们担心的少得多。实际上，只有以两位数格式存储年份的应用程序才会将年份变为 00，以表示时间倒退。尽管如此，许多应用程序开发人员还是做了很多额外的繁琐工作，以确保 2000 年到来时，他们的系统不会出现严重问题。
|
||||
|
||||
### Unix 时间何时会遇到问题？
|
||||
|
||||
在 2038 年之前，Unix 系统不会遇到 Y2K 类型的问题，直到如上所述存储的日期将超过其 32 位空间分配。但这距离现在已经只有 18 年了，内核开发人员已经在研究如何避免灾难。但现在开始恐慌还为时过早。
|
||||
|
||||
2038 年的问题有时称为 Y2K38 问题。我们必须在 2038 年 1 月 19 日星期二之前解决这个问题。如果问题到时候仍未解决，则该日期之后的系统可能会认为是 1901 年。解决该问题的一种方法是切换为日期/时间信息的 64 位表示形式。有些人认为，即使那样，也会有比听起来更复杂的问题。无论如何，恐慌还为时过早。并且，与此同时，也许在新年前夜演唱了《Auld Lang Syne》之后，你可以向 Unix 唱《生日快乐》歌了。Unix 50 岁了，这仍然是大事。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.networkworld.com/article/3511428/unix-is-turning-50-what-does-that-mean.html
|
||||
|
||||
作者：[Sandra Henry-Stocker][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[wxy](https://github.com/wxy)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://www.networkworld.com/author/Sandra-Henry_Stocker/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://images.idgesg.net/images/article/2017/10/birthday-cake-candles-100739452-large.jpg
|
||||
[2]: https://creativecommons.org/publicdomain/zero/1.0/
|
||||
[3]: https://www.networkworld.com/article/3440100/take-the-intelligent-route-with-consumption-based-storage.html?utm_source=IDG&utm_medium=promotions&utm_campaign=HPE20773&utm_content=sidebar ( Take the Intelligent Route with Consumption-Based Storage)
|
||||
[4]: https://www.facebook.com/NetworkWorld/
|
||||
[5]: https://www.linkedin.com/company/network-world
|
||||
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Reference in New Issue
Block a user