tubiz

Download Udemy course videos using youtube-dl

$ youtube-dl --list-extractors | grep udemy

Steps

1. Get link to the course to download. e.g. https://www.udemy.com/course-name/
2. Login into udemy website, save the cookie from chrome using Chrome (Cookie.txt)[1] export extension. Save it to file udemy-cookies.txt
3. Get the link of the video that you want to download. usually in format. Use the command provided below where you have to replace the {course_link} and {path_to_cookies_file} with respective paths.

# $ youtube-dl {course_link} --cookies {path_to_cookies_file}

rdeguzman

TLDR;
----------------------------------------------------
 st_transform(
    st_buffer(
      st_transform(st_geomFromText('POINT(145.228914 -37.92674)', 4326), 900913),
      50 --radius in meters
    ),
    4326
  )
----------------------------------------------------

alexellis

Convert sequence of JPEG images to MP4 video

ffmpeg -r 24 -pattern_type glob -i '*.JPG' -i DSC_%04d.JPG -s hd1080 -vcodec libx264 timelapse.mp4

• -r 24 - output frame rate
• -pattern_type glob -i '*.JPG' - all JPG files in the current directory
• -i DSC_%04d.JPG - e.g. DSC_0397.JPG
• -s hd1080 - 1920x1080 resolution

Slower, better quality

jdeathe

How to generate a self-signed SAN SSL/TLS certificate using openssl

Generating a self-signed certificate is a common task and the command to generate one with openssl is well known and well documented. Generating a certificate that includes subjectAltName is not so straght forward however. The following example demonstrates how to generate a SAN certificate without making a permanent change to the openssl configuration.

Generate a list of all required DNS names, (Note: CN will be discarded).

$ export SAN="DNS:www.domain.localdomain,DNS:domain.localdomain"

Brainiarc7

Spawning multiple ffmpeg processes with xargs:

On standard NVIDIA GPUs (Not the Quadros and Tesla lines), NVENC encodes are limited to two simultaneous sessions. The sample below illustrates how to pass a list of AVI files to ffmpeg and encode them to HEVC on two encode sessions:

$ find Videos/ -type f -name \*.avi -print | sed 's/.avi$//' |\
  xargs -n 1 -I@ -P 2 ffmpeg -i "@.avi" -c:a aac -c:v hevc_nvenc "@.mp4"

This will find all files with the ending .avi in the directory Videos/ and transcode them into HEVC/H265+AAC files with the ending .mp4. The noteworthy part here is the -P 2 to xargs, which starts up to two processes in parallel.

YuMS

#!/bin/bash
sudo add-apt-repository -y ppa:git-core/ppa
sudo apt-get update
sudo apt-get install git -y

bertt

// create table with srid=4326
CREATE TABLE testbert1
(
  id bigserial NOT NULL,
  description character varying(500),
  encodingtype integer,
  location public.geometry(geometry,4326)
)

// insert geometry

valyala

Optimizing postgresql table for more than 100K inserts per second

• Create UNLOGGED table. This reduces the amount of data written to persistent storage by up to 2x.
• Set WITH (autovacuum_enabled=false) on the table. This saves CPU time and IO bandwidth on useless vacuuming of the table (since we never DELETE or UPDATE the table).
• Insert rows with COPY FROM STDIN. This is the fastest possible approach to insert rows into table.
• Minimize the number of indexes in the table, since they slow down inserts. Usually an index on time timestamp with time zone is enough.
• Add synchronous_commit = off to postgresql.conf.
• Use table inheritance for fast removal of old data:

atenni

Use pg_dump to create a dev copy of a DB

Steps

1. Perform pg_dump -> gzip output -> save

   • pg_dump DB_NAME --username=DB_USER | gzip > /location/to/backup.gz
   • Note: if you get "FATAL: Ident authentication failed..." you'll need to look in pg_hba.conf. See below for more info.

2. Unzip -> import into new database

brock

# This is just a cheat sheet:

# On production
sudo -u postgres pg_dump database | gzip -9 > database.sql.gz

# On local
scp -C production:~/database.sql.gz
dropdb database && createdb database
gunzip < database.sql.gz | psql database