In Bash script, it is common that multiple small commands run together connected by pipes (|) and the whole command is quite long. For clarity, we may write the command in multiple lines. How to add comments for these long multi-line commands? In Bash, the content after # in a line is the comment. Using…
Perl 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….
Querying 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…
Hyperledger 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…
grep 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…
In 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…
We know compilers like gcc can do lots smart optimization to make the program run faster. Regarding functions call optimization, gcc can do tail-call elimination to save the cost of allocating a new stack frame, and tail recursion elimination to turn a recursive function to non-recursive iterative one. gcc can even transform some recursive functions…
Bash (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…
Since 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….
Conversion 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…
Thunderbird is a nice email client available on Linux and Windows. With the Lightning plugin, Thunderbird can support calendar functions well. Exchange is a widely used email and calendar/address book service software. Office 365 provide the cloud version of Exchange named Office 365 Exchange Online. Although Exchange Online provide IMAP for synchronizing emails, it provides…
After the recent iOS upgrading to version 13, many older iPhones such as iPhone 8 turn to be running slower, although there are many new features. New features and functions use more CPU/GPU/memory and the iOS may run slower. But are there any methods to make it run faster? After quite some research and testing,…
The Windows user name can be changed according to the user’s needs and requirement. The Windows 10 Windows Settings tool interface keeps changing after updates. It is a little hard to find out the tool to do the user name changing. One way to change Windows user name is to do it through the Computer…
Static 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…
Here is the case, the user can not write directly to the remote side’s directory, while the user can sudo on the remote side and write the directory with sudo. How to write to remote side with sudo in rsync? On the source machine, run the rsync command with –rsync-path="sudo rsync" added. For example, rsync…
If a team with many accounts share and manages the virtual machines under that same AWS accounts, it is a common practice to limit AWS EC2 accounts’ access to view or start all VMs yet stop only certain VMs. For example, one account has 50 VMs tagged “prod” while 25 VMs tagged “dev”. The developers…
How to do screen recording on Wayland in Linux? Many screen recorders do not work on the new Wayland. Using Green Recorder You may try Green Recorder which supports Wayland. Note: Green Recorder is no longer under development by the original author (Please check the project README for more details). It still works well for…
It is common that the root disk space is not enough when running a Virtual Machine in the cloud such as Amazon Web Service (AWS). The cloud storage usually provides tools or facilities to enlarge a virtual disk size. However, to make the Linux recognize and and use the enlarged disks without rebooting the OS,…
Reading: Years in Big Data. Months with Apache Flink. 5 Early Observations With Stream Processing: https://data-artisans.com/blog/early-observations-apache-flink. The article suggest adopting the right solution, Flink, for big data processing. Flink is interesting and built for stream processing. The broader view and take away may be to solve problems using the right solution. We saw many painful…
Google Drive is a nice cloud storage service. It provides a suite of nice online document spreadsheet and slide editors Google Docs, Google Sheets and Google Slides. The collaborative editing and full history tracking features of Google Docs are excellent. Google Drive gives 16GB free storage which is pretty much larger compared to other free…