Commands by eronisko (1)

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Get your external IP address if your machine has a DNS entry

Directory bookmarks
pushd and popd are your friends, but sometimes they're just incompatible with the way one works... Two shell functions: bm bookmarkname - "bookmarks" the current directory, just 'cd $BMbookmarkname' to return to it. forget bookmarkname - unsets the 'bookmarkname' variable. It isn't mandatory, they cease to exist when the session ends.

Randomize lines in a file
Works in sort (GNU coreutils) 7.4, don't know when it was implemented but sometime the last 6 years.

Securely destroy data on given device
Intentional hash in the beginning. May run a looong time. Wipes your data for real. Was meant to be /dev/urandom - I mistyped it. :-)

use jq to validate and pretty-print json output
the `jq` tool can also be used do validate json files and pretty print output `cat file.json | jq` available on several platforms, including newer debian-based systems via `#sudo apt install jq`, mac via `brew install jq`, and from source https://stedolan.github.io/jq/download/

Create the four oauth keys required for a Twitter stream feed
Twitter stream feeds now require authentication. This command is the FIRST in a set of five commands you'll need to get Twitter authorization for your final Twitter command. *** IMPORTANT *** Before you start, you have to get some authorization info for your "app" from Twitter. Carefully follow the instructions below: Go to dev.twitter.com/apps and choose "Create a new application". Fill in the form. You can pick any name for your app. After submitting, click on "Create my access token". Keep the resulting page open, as you'll need information from it below. If you closed the page, or want to get back to it in the future, just go to dev.twitter.com/apps Now customize FIVE THINGS on the command line as follows: 1. Replace the string "Consumer key" by copying & pasting your custom consumer key from the Twitter apps page. 2. Replace the string "Consumer secret" by copying & pasting your consumer secret from the Twitter apps page. 3. Replace the string "Access token" by copying & pasting your access token from the Twitter apps page. 4. Replace string "Access token secret" by copying & pasting your own token secret from the Twitter apps page. 5. Replace the string 19258798 with the Twitter UserID NUMBER (this is **NOT** the normal Twitter NAME of the user you want the tweet feed from. If you don't know the UserID number, head over to www.idfromuser.com and type in the user's regular Twitter name. The site will return their Twitter UserID number to you. 19258798 is the Twitter UserID for commandlinefu, so if you don't change that, you'll receive commandlinefu tweets, uhm... on the commandline :) Congratulations! You're done creating all the keys! Environment variables k1, k2, k3, and k4 now hold the four Twitter keys you will need for your next step. The variables should really have been named better, e.g. "Consumer_key", but in later commands the 256-character limit forced me to use short, unclear names here. Just remember k stands for "key". Again, remember, you can always review your requested Twitter keys at dev.twitter.com/apps. Our command line also creates four additional environment variables that are needed in the oauth process: "once", "ts", "hmac" and "id". "once" is a random number used only once that is part of the oauth procedure. HMAC is the actual key that will be used later for signing the base string. "ts" is a timestamp in the Posix time format. The last variable (id) is the user id number of the Twitter user you want to get feeds from. Note that id is ***NOT*** the twitter name, if you didn't know that, see www.idfromuser.com If you want to learn more about oauth authentication, visit oauth.net and/or go to dev.twitter.com/apps, click on any of your apps and then click on "Oauth tool" Now go look at my next command, i.e. step2, to see what happens next to these eight variables.

Restart openssh-server on your Synology NAS from commandline.
The correct way to restart openssh-server on your synology nas.

Convert JSON to YAML
Requires installing json2yaml via npm: npm install -g json2yaml (can also pipe from stdin) Ref: https://www.npmjs.com/package/json2yaml

Insert a line at the top of a text file without sed or awk or bash loops
Yet another way to add a line at the top a of text file with the help of the tac command (reverse cat).

Create a mirror of a local folder, on a remote server
Create a exact mirror of the local folder "/root/files", on remote server 'remote_server' using SSH command (listening on port 22) (all files & folders on destination server/folder will be deleted)


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