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  Create cron job on CentOS

These two days, I am building a website and deploying it on a VPS server which uses CentOS 5. I don't have cPanel or Plesk for my account, so I need to install and configure everything myself including Apache, PHP, MySQL and FTP server, also today's topic cron job. Since my website has a ranking algorithm to calculate the rankings of each link and update the ranking on database and I need to calculate the rankings every 5 minutes, so I think to use cron jobs. Here are what I have done which may ...

   cron job,crontab,CentOS,linux,php,example     2012-06-11 09:23:45

  Understanding How is Data Stored in RDBMS

We all know that DBMS (database management system) is used to store (a massive amount of) data. However, have you ever wondered how is data stored in DBMS? In this post, we will focus on data storage in RDBMS, the most traditional relational database systems. Physical Storage Data can be stored in many different kinds of medium or devices, from the fastest but costy registers to the slow but cheap hard drives, or even magnetic tapes. Nowadays, IaaS providers such as AWS...

   RDBMS,DATABASE     2019-02-04 09:25:36

  A Sip of Go Log

Logging is indispensable in any code that we need its support both in debugging and in statistics. However, a package that filled withfmt.Println/fmt.Printf printing various messages can never be considered a read-to-be-adopted package, which can be optimized by a simple change, using Golang’s native log package to print information to standard output or to a file. Then, how to apply the log package? Are there any limitations? If so, can we seek open-source packages? Let&rsq...

   GOLANG,LOGGING     2022-06-16 05:43:24

  Some hidden XSS injection vulnerabilities

XSS injection refers to a Web page generates some unexpected executable js codes based on user input  and these executable codes are executed by web browser,i.e, the source code sent to web browser by the server contains some illegal js codes, and these illegal js codes are related to user's input. Common XSS injection vulnerabilities can be fixed with some functions such as htmlspecialchars(escaping HTML special characters) and strip_tags() or similar, but there are some hidden XSS injecti...

   XSS,PHP,Security,Code,JavaScript     2012-08-27 20:32:08

  Understand unsafe in GoLang

Before going to understand unsafe package in GoLang, the first thing needs to talk about is the pointer in GoLang. If you have a background of C language, you must know what pointer means and its usage. With pointer, you are free to operate any data at memory level which means you have great power, but this means that you have great responsibility as well. That's why it might be considered unsafe in lots of cases. Take a look at a simple example of doubling an integer. package main import "fmt"...

   GOLANG,UNSAFE,ZERO-COPY     2020-03-14 23:18:00

  Emacs adventures

I have been using Emacs for over a year now. I actually didn’t learn a lot when I started using it (just the basics to get going and then some relatively common keyboard shortcuts), but lately I have been reading and learning much more about it. I’m so grateful by everything I’ve learned from different people on the net that I wanted to share a couple of things I’ve learned, and a simple major mode for editing AsciiDoc documents. As a long-time VIM user, I f...

   Editor,Linux,Emacx,VIM,Shortcuts     2011-11-30 11:56:49

  One reason why mcrypt responds slowly

This morning one colleague came over and talked about one script which used mcrypt responded very slowly, the server configurations are fine. But the reason for the slowness is unknown. Here is one script which reproduces the issue: <?php $dmcryptText = "dummy"; $key = "foobar"; $size = mcrypt_get_iv_size(MCRYPT_BLOWFISH,MCRYPT_MODE_ECB); $iv = mcrypt_create_iv($size); //Take care $m = mcrypt_ecb(MCRYPT_BLOWFISH, $key, $dmcryptText, MCRYPT_DECRYPT, $iv); var_dump($m); When 20 requests of&...

   SOLUTION,SLOW,MCRYPT,RESPONSE,PHP     2012-09-27 12:03:16

  Python: calculate lighter/darker RGB colors

Many times color palettes have lighter and darker variations of the same color. This may be used to convey relative importance, or for something as simple as a gradient. Usually the designer will specify both colors. However, if you have a site that needs to allow user configurable styling, you may not want to ask the user for two variations of the same color. Here is some Python code to take a single color in RGB, and output an artitrarily lighter or darker variation of the same color...

   Python,RGC color,Calucaltion lighter/darker     2012-02-13 05:29:22

  How to check which Ohai plugin hangs in chef client run

Ohai plugins are very important components in chef client which aims to provide resource management automation on a server. The data discovered by Ohai plugins are describing the current state of the server and they will be used to maintain the server in a desired state. Each Ohai plugin discovers a specific pierce of information about the server such as cpu, memory, middleware etc. However, there are rare occasions(well I am a bit optimistic here) someone may find that the chef client...

   HOW TO,CHEF-CLIENT,OHAI,UPTIME,HANG     2017-12-24 22:09:59

  In-memory key-value store in C, Go and Python

Subtitle: Wow Go’s net library is fast On paternity leave for my second child, I found myself writing an in-memory hashmap (a poor-man’s memcached), in Go, Python and C. I was wondering how hard it would be to replace memcached, if we wanted to do something unusual with our key-value store. I also wanted to compare the languages, and, well, I get bored easily! The code is on github as Key-Value-Polyglot. Each version implements enough of the get and set commands from the mem...

   key-value,Memory,C,Python,Go     2012-03-21 09:21:51

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