R is a language and environment for statistical computing and graphics, providing a wide variety of statistical and graphical techniques. The R environment is open source software under GPL. R has rich software packages and is widely used for statistical analysis. RStudio Server is an R integrated development environment (IDE) that provides many useful features
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Linux Kernel 4.19.70 Release
Posted onThis post summarizes new features, bugfixes and changes in Linux kernel release 4.19.70. Linux 4.19.70 Release contains 95 changes, patches or new features. In total, there are 101,521 lines of Linux source code changed/added in Linux 4.19.70 release compared to Linux 4.19 release. To view the source code of Linux 4.19.70 kernel release online, please
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Compress PNG Images on Linux
Posted onPNG images already use DEFLATE data compression algorithm involving a combination of LZ77 and Huffman coding. But the PNG images can be further compressed by removing non-important metadata or using lossy compression to save storage space and/or data transfer bandwidth. In this post, we introduce 2 compression ways with tools available on Linux. Lossless compression
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Redirect Feed Links to follow.it using .htaccess
Posted onFeedburner used to a powerful tool for RSS feeds publishing and subscriber management. However, feedburner will unlikely leave its maintenance mode because there has been no new features yet less features for quite some years. But RSS feed is still an important part of the Web supported by many software such as WordPress. follow.it is
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How to Match Multiple Lines using Regex in Perl One-liners
Posted onPerl one-liners with perl’s regular expression statement can be a very powerful text processing tools used as commands in a terminal or a script. By default, the input to the perl one-liner with -p or -n options is passed line by line. However, when we want to match multiple lines, it gets us some trouble.
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How to Query Transaction By ID in Hyperledger Fabric 2.0
Posted onQuerying transaction content out from a blockchain network is a common practice used by common scenarios like exploring the blockchain history or verifying the blockchain transaction content from a known ID. In Hyperledger Fabric, the transaction can be queried using a special system chaincode QSCC (Query System Chaincode) which is for ledger and other Fabric-related
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Blockchain Platforms Introduced, Each in One Sentence
Posted onThis post lists some general- and special-purpose nowadays available with a short description in one sentence. Readers can have a quick understanding of what a blockchain network is built for and what uniqueness that blockchain has. I also give links to beginner friendly resources as learn materials. General purpose blockchains Blockchains for general purpose usage.
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How to Install Hyperledger Fabric 2.0 in Ubuntu 18.04
Posted onHyperledger Fabric is a consortium blockchain system. It’s performance is relatively good and its modular architecture enables it to be usable in many scenarios. Hyperledger Fabric itself has rich documents and samples of test networks. For beginners, deploying a new network for trying and testing still consumes quite some time. In this post, we will
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Grep 2 Lines using `grep` Command in Linux
Posted ongrep is excellent to match patterns from STDOUT/text files in command line or scripts. It’s handy. Sometimes, our problem is more complex than finding a keyword from a file. On a first thought, it may sound impossible using grep for such complex problems. But grep can be quite powerful than we thought. Today, let’s check
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How to Install Go 1.13.x on Ubuntu 18.04
Posted onIn Ubuntu 18.04 LTS, the default Go lang version is 1.10. For compatibility reason, the Ubuntu LTS will usually keep the major release version numbers for packages. However, many applications, such as Hyperledger Fabric 2.0, require a newer version of Go. In this post, let’s take a look at how to install a system level
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Bash Learning Materials
Posted onBash (GNU Bourne-Again SHell) the default shell for many Linux distributions. It is very common for scripting languages in Linux. Bash is easy and straightforward for writing small tools. However, as most tools, it has its grammars that could easily cause bugs if they are not used correctly. Here I summarize a list of good
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How to Install Wine 32-bit on CentOS 8
Posted onSince version 7, RHEL and CentOS only have 64 bit versions. For some reasons, it’s better to run many Windows applications under 32 bit wine. Like How to Install Wine 32-bit on CentOS 7, this post introduce how to install 32-bit Wine on CentOS 8. Most of the mechanisms are similar yet there are differences.
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How to Convert Integers to Strings and Strings to Integers in PHP
Posted onConversion from integer to string and from string to integer are common operations in most applications such as C++. PHP has its uniqueness in language and standard library design. In this post, we will check methods to convert integers to strings and vice versa. Convert string to int in PHP You can cast a string
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How to mirror a website using wget on Linux?
Posted onHow to mirror a website using wget on Linux? If the command can filter only specific file extensions, such as pdf and docx, it will be much better too. To download all PDF files from https://example.org/path/ as an example, you may use this command: wget –mirror \ –convert-links –no-parent –quiet \ –adjust-extension -A pdf \
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How to Statically Link OCaml Programs
Posted onStatic linking is preferred for some cases although it has its own various problems. Static building/linking is not always possible for some languages on some platform. For OCaml, the answer to this question is yes. In this post, we will introduce 2 methods to statically linking OCaml: static linking with runtime glibc required and static
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How to get date and time using date command from another timezone in Linux?
Posted ondate command on Linux gets the date and time in the system timezone. But how to get date and time using date command from another timezone in Linux? You can make date print the time of another timezone by setting the TZ environment variable. For example, export TZ=Hongkong; date Sat Dec 1 09:39:13 HKT 2018
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Installing Zlib Library in Ubuntu Linux
Posted onOn Ubuntu (18.04 and 20.04), installing zlib reported unable to locate package zlib: $ sudo apt install zlib Reading package lists… Done Building dependency tree Reading state information… Done E: Unable to locate package zlib How to install zlib in Ubuntu? Install zlib in Ubuntu from Ubuntu package repo In Ubuntu, the zlib package is
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Thunderbird Addons to Make Thunderbird Easier to Use
Posted onThunderbird is powerful and feature rich. But different users have different needs and it is not feasible to include all features into the base software, where a plugin system shines. Thunderbird, similar to Firefox from Mozilla, supports addons/plugins and has a large ecosystems. Here, we will introduce several addons to Thunderbird that make Thunderbird easier
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Handling Sparse Files on Linux
Posted onSparse files are common in Linux/Unix and are also supported by Windows (e.g. NTFS) and macOSes (e.g. HFS+). Sparse files uses storage efficiently when the files have a lot of holes (contiguous ranges of bytes having the value of zero) by storing only metadata for the holes instead of using real disk blocks. They are
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How to divert connection or packet before routing decision entering the default
Posted onbefore the packets ports (443) entering the firewall i would like to divert incoming packet of server (443) to input chain goes to FORWARD chain<br> so thats the incoming packets 100.43.xx.xx –sport 443 are send it to FORWARD instead of input chain<br> how to configure this in OUTPUT,FORWARD,POST AND PREROUTING CHAIN and this is my
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