Hot For Coding
关于Linux动态链接so文件

在Linux下写C程序时,常常有很多基础通用重复性的代码,最常见的比如重复使用CURL库创建HTTP请求,动态链接库就为了解决这个问题,可以把重复性的函数库单独编译成so文件,然后多个程序可以共享一个so文件提供的函数库

Linux内置了一些常见的类库so文件,我们也可以自己编译自己需要的类库文件放到/usr/lib目录下,使用动态链接库有以下优势

  • 提升编译速度,类库部分不需要重新编译
  • 更容易升级部分功能,比如所有程序依赖curl库,那么如果curl可以单独升级而不用重新编译程序
  • 由于源码体积减少,所以编译出来的可执行文件体积也小

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Nginx定义404页面

前几天,一朋友出程序出问题却怎么查都没看出问题,于是让我帮它看看。其实它是Ajax请求了很多个模板,然后把模板写到页面中。关键是所有请求的页面都是200正常状态码返回,表面上看没什么问题,实际上有些请求虽然返回200状态码,但给回的状态码是200。WebServer是Nginx,我觉得有可能配置了Nginx的404错误页面,虽然请求不存在的资源可以成功返回404页面,但返回状态码确是200。

404.html

This is 404 page.

请求一个不存在的页面:

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Django自带加密模块的使用

在Win平台开发Python项目往往因为加密模块不能使用crypt加密模块而感到蛋疼,这次使用Django在Win平台开发项目就又为这个加密模块而发愁。但考虑到Django有用户验证模块,证明它已具备跨平台的加密模块。于是阅读文档,在https://docs.djangoproject.com/en/1.6/topics/auth/passwords/页面发现有这样一段话

Manually managing a user’s password
The django.contrib.auth.hashers module provides a set of functions to create and validate hashed password. You can use them independently from the User model.
check_password(password, encoded)
If you’d like to manually authenticate a user by comparing a plain-text password to the hashed password in the database, use the convenience function check_password(). It takes two arguments: the plain-text password to check, and the full value of a user’s password field in the database to check against, and returns True if they match, False otherwise. Changed in Django 1.6:
In Django 1.4 and 1.5, a blank string was unintentionally considered to be an unusable password, resulting in this method returningFalse for such a password.
make_password(password[, salt, hashers])
Creates a hashed password in the format used by this application. It takes one mandatory argument: the password in plain-text. Optionally, you can provide a salt and a hashing algorithm to use, if you don’t want to use the defaults (first entry of PASSWORD_HASHERS setting). Currently supported algorithms are: 'pbkdf2_sha256', 'pbkdf2_sha1', 'bcrypt_sha256'(see Using bcrypt with Django), 'bcrypt', 'sha1', 'md5', 'unsalted_md5' (only for backward compatibility) and 'crypt' if you have the crypt library installed. If the password argument is None, an unusable password is returned (a one that will be never accepted by check_password()).

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IE11打不开网页,菜单项变灰

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IE11浏览器突然打不开任何网页

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点击设置按钮大多数设置都是灰的:

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到 控制面板 > 程序和功能 > 打开或关闭window功能 中IE11取消勾选,确定

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重启,在进去把它勾选回去安装,重启,打开IE11依旧还是没有解决问题。从官网下载IE11安装包进行安装却总提示已安装最新版本。

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MySQL导入sql脚本错误 2006 - MySQL server has gone away

MySQL导入sql 10M脚本时出错,如图

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Error occured at:2014-03-24 11:42:24
Line no.:85
Error Code: 2006 - MySQL server has gone away

最终找到原因,原来是MySQL导入大批量数据的时候超出了默认允许最大的数据包所以就提示2006 - MySQL server has gone away

于是找到my.cnf,在[mysqld]加入:

max_allowed_packet=300M
wait_timeout=200000
interactive_timeout = 200000

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Django1.6访问static内容提示编码错误

今天用Django搭建一个环境,在访问的时候感觉有点怪

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感觉页面CSS似乎没有被加载进来,于是单独访问某个CSS文件结果浏览器提示

A server error occurred. Please contact the administrator.

控制台

Traceback (most recent call last):
  File "D:\Python27\lib\wsgiref\handlers.py", line 85, in run
    self.result = application(self.environ, self.start_response)
  File "D:\Python27\lib\site-packages\django\contrib\staticfiles\handlers.py", line 68, in __call__
    return super(StaticFilesHandler, self).__call__(environ, start_response)
  File "D:\Python27\lib\site-packages\django\core\handlers\wsgi.py", line 206, in __call__
    response = self.get_response(request)
  File "D:\Python27\lib\site-packages\django\contrib\staticfiles\handlers.py", line 58, in get_response
    return self.serve(request)
  File "D:\Python27\lib\site-packages\django\contrib\staticfiles\handlers.py", line 51, in serve
    return serve(request, self.file_path(request.path), insecure=True)
  File "D:\Python27\lib\site-packages\django\contrib\staticfiles\views.py", line 41, in serve
    return static.serve(request, path, document_root=document_root, **kwargs)
  File "D:\Python27\lib\site-packages\django\views\static.py", line 61, in serve
    content_type, encoding = mimetypes.guess_type(fullpath)
  File "D:\Python27\lib\mimetypes.py", line 297, in guess_type
    init()
  File "D:\Python27\lib\mimetypes.py", line 358, in init
    db.read_windows_registry()
  File "D:\Python27\lib\mimetypes.py", line 258, in read_windows_registry
    for subkeyname in enum_types(hkcr):
  File "D:\Python27\lib\mimetypes.py", line 249, in enum_types
    ctype = ctype.encode(default_encoding) # omit in 3.x!
  File "D:\Python27\lib\encodings\utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xb0 in position 1: invalid start byte

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MySQL5.6 Using a password on the command line interface can be insecure

最近把MySQL从5.5升到5.6以后,mysqldump居然不好用了,提示

[root@qttc ~]# /usr/local/mysql/bin/mysqldump  -uroot -proot db > bak.sql
Warning: Using a password on the command line interface can be insecure.

这让人有点奇怪,5.5用的一直都很爽,到5.6居然说命令行方式写密码不安全?那密码写哪呢?

在官网文档找到了原因

MySQL users should use the following guidelines to keep passwords secure.
When you run a client program to connect to the MySQL server, it is inadvisable to specify your password in a way that exposes it to discovery by other users. The methods you can use to specify your password when you run client programs are listed here, along with an assessment of the risks of each method. In short, the safest methods are to have the client program prompt for the password or to specify the password in a properly protected option file.

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SWFUpload上传提示Security Error 2049

很早之前,我写过一篇基于PHP版本的SWFUpload上传组件的文章,最近老是收到不少朋友询问SWFUpload的问题,决定再整理一些最常见的问题整理出来。

点击hello弹不出选择文件对话框

这是由于你没有基于HTTP协议访问引起的,你可以把它放到WebServer里试一试,比如Nginx,Apache,Tomcat等等,然后使用http访问页面

上传文件提示Security Error 2049

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这是很多朋友经常犯的错误,JavaScript有跨域问题,Flash做为前端组件自然也存在跨域问题,解决此问题的方法是在upload域下创建如下文件:

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Java sleep和yield区别

yield和sleep都是作用于当前线程

yield方法会临时暂停当前正在执行的线程,让有同样优先级等待的线程有资源执行。如果没有正在等待的线程,或者所有正在等待的线程的优先级都比较低,那么该线程会继续运行。执行了yield方法的线程什么时候会继续运行由线程调度器来决定,不同的CPU可能有不同的行为。yield方法不保证当前的线程会暂停或者停止,但是可以保证当前线程在调用yield方法时会放弃CPU。

所以总结下来

  • yield和sleep都不释放锁
  • sleep只是暂停,之后继续
  • yield是让出CPU资源,等待下一次资源调度继续

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CentOS开机卡在进度条的解决方法

CentOS开机的时候卡在进度条一直进不去

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这看不出开机启动卡在哪里,只好重启按住"e"键,进入启动菜单

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接着按e进入编辑第一项

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然后移动到第二项kernel...接着按e进入编辑

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去掉rhgb quiet字样

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