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  Permutation algorithm with JavaScript

In secondary school, we have learned permutation. Basically, for n numbers, the number of permutations for these n numbers can be calculated to n! which is called 'n factorial'. But to display all the permutations on the screen, we need to use a recursive function. The problem is how to write this function.  Next I write a program to display the permutations for n numbers with JavaScript. First, we need to understand that from these n numbers, we can first take any one number from it, and t...

   JavaScript,Permutation,Algorithm,Impleme     2011-09-21 12:02:35

  Replacing small C programs with Haskell

C is the classic go-to tool for small programs that need to be really fast. When scripts.mit.edu needed a small program to be a glorified cat that also added useful HTTP headers to the beginning of its output, there was no question about it: it would be written in C, and it would be fast; the speed of our static content serving depended on it! (The grotty technical details: our webserver is based off of a networked filesystem, and we wanted to avoid giving Apache too many credentials in ca...

   C,Haskell,Small program     2012-01-03 10:51:39

  Use DTrace to diagnose gdb issues

A few days ago, I installed the newest 64-bit gdb program (version 7.7.1) on Solaris 10 (X86_64 platform) to debug programs. After playing with the gdb a day, I found 2 issues about gdb:(1) The "set follow-fork-mode child" command doesn't take effect. By default, after the parent process forks the child process, the gdb will track the parent process, so this command can make gdb begin to follow the child process. But this command works OK on Linux.(2) The gdb can't parse the 32-bit application c...

   DTrace, debug, gdb, UNIX     2014-06-28 05:11:20

  IE ActiveX(”htmlfile”) Transport, Part II

In my last post I discussed using the ActiveX(”htmlfile”) technique to provide a usable streaming transport in Internet Explorer. The solution I provided will work, but since writing the last article I’ve made significant progress in understanding why IE behaves the way it does with respect to the streaming transport. The previous solution amounted to creating an array of messages, pushing messages on that array from the htmlfile iframe, and popping messages off of the array i...

   IE,Http,Streaming,htmlfile,Transport,Act     2011-09-05 04:07:02

  Generate certificate with cRLDistributionPoints extension using OpenSSL

In an X509 certificate, the cRLDistributionPoints extension provides a mechanism for the certificate validator to retrieve a CRL(Certificate Revocation List) which can be used to verify whether the given certificate is revoked.   A cRLDistributionPoints extension can contain one or more DistributionPoints where the CRL can be retrieved from. Each DistributionPoint consists of three fields,each of which is optional: distributionPoint : it contains either a SEQUENCE of general...

   X509,OPENSSL,CERTIFICATE,CRLDISTRIBUTIONPOINT,EXTENSION     2015-10-22 03:41:11

  Send email from Ubuntu command line

First install exim4 and exim4-config using the package manager then install mailx sudo apt-get install mailutils and follow the prompts once this is set up use the command “mail” to check your mail. if you would like to send mail type “mail” followed by the email address to mail it to eg mail me@examplecom enter the subject and press enter the body and keep pressing enter as many times as you need to, when your body is finished, press “Ctrl” and “D" toge...

   Ubuntu,Email,Command line,mailutils     2011-04-25 15:58:10

  Ruby net-scp cannot scp multiple files with asterisk(*)

net-ssh/net-scp is a Ruby gem which can be used to scp files between different *nix machines. It's similar to how the *nix scp command. It can be used to scp a file or a directory. However, it seems it has some problem to scp multiple files using pattern *. For example, below script is supposed to download all files from remote directory to local directory: require 'net/scp' host = 'testmachine' login = 'testaccount' password = "testpassword" remote_path = '/tmp/remote...

   NET-SCP,RUBY,ASTERISK,MULTIPLE FILES     2016-10-20 03:00:13

  JavaScript cross domain request solution

1. What is cross domain? We may often using AJAX to request data from other domain, now we will have cross domain request issues. It's because JavaScript only allows to request data from the same domain because of security consideration. In short, same domain strategy means a piece of code can read data from the same source, the same source here means the combination of the same domain, protocol and port number. For example: URLDescriptionAllow communication? http://www.a.com/a.js http:/...

   AJAX,cross domain,security     2013-03-13 20:04:52

  Build a Kubectl Plugin from Scratch

by author The command-line tool kubectl is indispensable when using Kubernetes. You need it to query related Pod and Service information both in developing or performing some maintenance operations, such as events, scale, rolling update, etc. However, when using kubectl, there are many inconveniences. Though Kubernetes is officially maintaining kubectl¹, and you can submit the problems, improvement, and even PR in its Github Issues, you still have to wait long before its release. The m...

   KUBENETES,KUBECTL,PLUGIN,GOLANG     2020-12-02 03:43:16

  What Level Programmer Are You?

Everybody's talking about how programming is the skill that we all are going to need. [Except those folks who might feel that most programming could be turned into wizard-like tools. Insert long discussion about Strong AI.] But what's a programmer? Is the guy who set up his own Apache Web Server a programmer? How about the guy who created a complex Excel spreadsheet? The guy who made his own RPG level? Minecraft players? When we say "Everybody is going to have to know programming" what, e...

   Programmer,Skill,Level,Criteria     2012-02-08 10:07:41

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