August 31, 2020

openssl ssl version number interpretation

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in file: usr/include/openssl/opensslv.h     of openssl source code.                                                                         ...
August 16, 2020

ffmpeg command for generating Amazon Ads video

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  ffmpeg -i videoSharingFinalOutput.MOV -profile:v main -r 25 -vf scale=1280:720 output.mp4
July 21, 2020

Golang short variable declaration gotcha

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Golang allows short variable declaration in the form of i:=0 , which defines a integer variable i . Golang also allows multi-variable short...
June 26, 2020

Golang range gotcha

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In golang, when you range through an array of elements as in the following: // THIS CODE IS WRONG; DO NOT USE THIS for i,v := range element...
June 12, 2020

Vim typescript jump-to-definition

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Use vim 8.1 or newer (in older version of vim, tagstack doesn’t work with the solution below) Install ALE https://github.com/dense-analys...
June 11, 2020

AWS API Gateway Wildcard Path

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In API Gateway configuration, typically one specifies an complete API Path, such as /api/v1/fruits/list . Sometimes, it may be necessary to ...
May 4, 2020

gitconfig

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[user] name = MY NAME email = MY EMAIL [core] editor = vim whitespace = cr-at-eol [merge] tool = vimdiff [alias] vim...
November 6, 2019

AWS API Gateway can be expensive

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As of 2019/11, AWS charges $0.25 per million connection minutes. That sounds very innocent, but is it? If your business grows and you have ...
October 30, 2019

AWS VPC: Private Subnet vs Public Subnet

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In AWS, a private subnet is defined as a subnet that doesn’t have a direct route to the Internet. It is only accessible from within the subn...
October 17, 2019

R ggplot2 geom_bar order

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In R, to plot a pie chart using a dataframe as the data source, one would use geom_bar first to plot a bar graph, and then use coord_polar ...
October 15, 2019

jq

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jq is a very useful tool to process JSON. The idea of jq is centered on the idea of pipe and data stream . Note below that a JSON entity...

IPv6 DNS server

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2600:: 2600::1 2600::2
September 25, 2019

SSH: How to identify which key to use when AgentFowarding is in use

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https://superuser.com/questions/273037/using-the-identityfile-directive-in-ssh-config-when-agentforwarding-is-in-use  ...
September 8, 2019

Lego EV3 Sound file .rsf format

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Lego EV3 support play sound files, and the Lego programmer software comes with many built-in sound files. If you want to add new sound files...
August 23, 2019

Instant file sharing without logging in

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1. https://sharedrop.io  Web-RTC based; Local LAN transfer doesn't leave LAN 2. https://file.pizza  HTTP streaming and Web-RTC based. ...
July 30, 2019

Windows 10 spotlight image files location

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%userprofile%\AppData\Local\Packages\Microsoft.Windows.ContentDeliveryManager_cw5n1h2txyewy\LocalState\Assets https://www.howtogeek.com/2...
July 18, 2019

Search Linux Kernel to find out when a feature was added

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Use the LKDDB (Linux Kernel Driver DataBase): https://cateee.net/lkddb/web-lkddb/IP_SET_HASH_IPMAC.html Search a CONFIG_xxx and it will ...
May 15, 2019

TCP socket send buffer deep dive

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A typical TCP socket send buffer is composed of three parts: unacked-bytes, unsent-bytes, and free-buffer. ...
May 9, 2019

Enable user-id based packet routing on Mac OS

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If you would like to route all socket (TCP/UDP) traffic from processes running by a particular user on a Mac OS to be routed differently, y...
February 26, 2019

keep ssh running in background for tunneling

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1. write the following script to a file, named "tunnel.sh" and make it executable (make sure user has public auth enabled on remot...