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社会化海量数据采集爬虫框架搭建 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...取，他的好处可以支持规整网页数据抓取。我们使用的是google插件 XPath Helper，这个玩意可以支持在网页点击元素生成xpath，就省去了自己去查找xpath的功夫，也便于未来做到所点即所得的功能。正则表达式补充xpath抓取不到的数...
How to select a single field for all documents in a MongoDB collection?
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Can't seem to Google this, so worth a shot. Do you have to explicitly exclude all the fields that you don't want? Say you only want one field but the document has 10 you have to explictly set 0 for 9 of them? Edit: Nevermind, excluding _i...
Validating URL in Java
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For the benefit of the community, since this thread is top on Google when searching for
"url validator java"
Catching exceptions is expensive, and should be avoided when possible. If you just want to verify your String is a valid URL, you can use the UrlValidator class from the Apach...
Adding List.add() another list
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What is the $? (dollar question mark) variable in shell scripting? [duplicate]
...to understand someone else's code. What is the $? variable hold? I can't Google search the answer because they block punctuation characters.
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Timing a command's execution in PowerShell
...eful to someone else. gist.github.com/2206444 -- Example: time { ping -n 1 google.com } -Samples 10 will run the command 10 times and return the average, minimum and maximum time taken. You can add -Silent to swallow STDOUT.
– joshuapoehls
Mar 26 '12 at 18:11
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Show percent % instead of counts in charts of categorical variables
...s = percent) ## version 3.0.0
This question is currently the #1 hit on google for 'ggplot count vs percentage histogram' so hopefully this helps distill all the information currently housed in comments on the accepted answer.
Remark: If hp is not set as a factor, ggplot returns:
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Check if object exists in JavaScript
...ct, the alert would be shown.
I have an example in my site.
https://sites.google.com/site/javaerrorsandsolutions/home/javascript-dynamic-checkboxes
How can I setup & run PhantomJS on Ubuntu?
...rent version (1.5) there is no need to install either qt or xfvb. See code.google.com/p/phantomjs/wiki/Installation
– michelpm
Jun 4 '12 at 21:21
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Running code in main thread from another thread
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This answer is fine for most people arriving from Google.
– xjcl
Aug 22 at 15:16
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