TIL

I created this to keep log of things I learn on daily basis when working on different problems.

Extract Links using CURL

xargs -n 1 curl -sL < 2018.txt | grep -Eo "<title>.*</title>" The command to extract links using curl
curl -sL https://news.ycombinator.com/item\?id\=18740939 | grep -Eo 'href="(https|http):[^\"]+"' Command to extract the links from hackernews
grep -aEo "<title>.*</title>" 

-a option to process binary file link to sol

use ``` backticks to run a command in bash

Counting files in directory

To count specific files in the directory you can use the following command


ls *.<file_extension> | wc -l

lets say if you want to see how many css files you have in a directory you might use this command as


ls *.css | wc -l

Generating a Grub File

We can use this command to generate a grub configuration file.

sudo grub-mkconfig -o /boot/grub/grub.cfg

As grub-mkconfig scans hardrives for bootable operating systems such as windows, mac or linux distros

Assigning Programs to Workspaces

To open programs on specific windows when using i3 window mananger add the following to the i3 config

assign [class="<use your program name here e.g. - Firefox>"] $workspace <eg 5>

After adding to the config make sure to refresh i3-msg reload

Resize images on Commandline

In order to resize images using command you can use the convert command.

convert img.jpg -resize 200x200 img-1.jpg and you can also convert to different extenstions using convert command. convert img.png img.jpg

If you don't have convert installed you can install from a package manager.

Setting up printer using CUPS

To add a printer on linux use CUPS.

Access the web admin http://localhost:631/

Killing port on Linux

fuser -k <port_name>/tcp use fuser to kill specific ports on linux

Revert Chmod

chmod -x allows you to revert the executable created by chmod +x

Enabling BLuetooth on Linux

In order to enable the bluetooth in Linux especially when using a command line, do the following

sudo systemctl enable bluetooth.service

To stop the bluetooth service

sudo systemctl enable bluetooth.service

Then you can use bluetoothctl to connect or pair devices using bluetooth

Saving a file with root permissions

In order to save a file with root permission using vim you can do

:w !sudo tee %

Vim Notes

These are learning notes when learning vim key bindings

Vim has three modes

  • INSERT : You can use i for the insert mode
  • VISUAL : You can use v for visual mode.
  • NORMAL MODE : just press ESC to get into normal mode

Basic Navigation

  • In order to get into insert mode use i.
  • gg takes you to the first line of the document.
  • Shift-G takes you to the last line of the document.
  • You can also move to the specfic line by <line number> G.
  • you can use x to delete a character.
  • you can use u to undo a change.
  • you can also specific the number of characters you want to delete <num of char> x
  • to delete a whole word use dw.
  • to delete a line use dd.
  • to number of lines use <num of lines> dd.
  • to move one word at a time w.it goes to the beginning character of the word.
  • to move using last character use e.
  • to move number of words use <num of words> w for example 10 w this moves 10 words.
  • to move backward a word you can use b.
  • to move number of words backward use <num of words> b 10 b.
  • use 0 to go to the beginning of the line.
  • you use p to put a line to desired line number for example you can dd a line then 10 G and then do p to put the line on line 10
  • You can replace a word or a character by using r.
  • Change to get into change command you can change words by using ce to get the end of the word.
  • c$ to change the entire line
  • navigating using command f:(forward <to_word>) and uppercase does this in reverse. for example,fe will take to the character e and Fe will take you backward.
  • to delete a specific line you can do :<line>d

Different Insert Modes.

  • A takes to the end of the line and enters in to insert mode.
  • a takes you into insert mode.
  • S deletes the entire line and enters you into the insert mode.
  • s delete the character and enters you into the insert mode.
  • o enters you into the insert mode in the next line.
  • O enters you into the insert mode in the preceding line.
  • C deletes the entire line c$
  • d$ deletes everything from the cursor to the end of the line. You can use D to do the same thing.

Yanking

Its the copy command in the vim editor

  • to copy a word just use yw you can paste by using p.
  • yy to copy the entire line.
  • y$ to copy from the cursor to the end of the line.
  • P puts to the preceding line

Searching through the code/doc

  • / search forward in the doc. then hit n to goto the next instance.
  • ? searches backward in the doc.

Replacing

  • You can :%s/oldstring/newstring/g to replace a word
  • you can also give line numbers 1,2s/old/new/g
  • :%s/old/new/gc gives a prompt.

Executing a command in vim

  • ! <cmd> to execute a command
  • cntrl-d to see what commands are available

note: you can enable vim mode in zsh by adding bindkey -v to zshrc

VIM Macros

  • You can record vim macros by using the q key and followed whatever key you want to assign that macro to.
  • to run the macro number of occurences and key where you saved the macro.

Vim Splits

  • :split does horizontal split :sp
  • :vsplit does vertical split :vs
  • cntrl-w ccloses the split.
  • you can also specific the height when doing a split 10sp <filename>
  • you can do cntrl-w R to swap the split
  • cntrl-w j and cntrl-w k moves you up and down
  • cntrl-w h and cntrl-w l moves you left and right
  • you can also resize the splits vertical resize +5 or resize +5 for horizontal split.
  • you can also open terminal in vim. especially in split :vs | :terminal

Command Mode in Vim.

  • you can run shell commands in vim :! ls this will print the files of your directory.
  • you can also read the outputs of the command and add it to the document :read !date
  • you can also use ranges when replacing the text 11,16s/old/new/g
  • :g/vim/d this will delete vim from every line where it finds the word.
  • !g/vim/d this will delete that will delete that's not vim.
  • g/^/pu/ =\"\n\" puts spaces.
  • g/<word>/m$ moves the lines containing that word to the end of the file

Vim Tabs

  • You can edit a file in a new tab by tabedit <filename>
  • you can gt to cycle through the tabs.

Few Notes

  • ddp allows you to swap a line.
  • g/<word>/+1m-2
  • > allows you to indent 111,114>
  • :{range} '<,'>' norm A" adds " at the end of the line.
  • :{range} '<,'>' norm I" adds " at the beginning of the line.
  • cgn allows you to change the next instance when doing a search.
  • you can also set abbreviations :ab rtfm Read The Friend Manual and use cntrl-v if you don't want to expand it.
  • Read commandline commands into vim :r !ls

Deleting Git Branches Locally and Remotely

In order to delete a branch on git locally you can use git branch --delete <branchname> and if you want to do it remotely you can do

git push --delete <branchname>

Deleting Git Commit History

To delete git commit history do the following

  • git checkout --orphan <new_branch_name>
  • git add -A
  • git commit --all -m "a message"
  • git branch -D <delete the main branch>
  • git branch -m <rename the new branch to main branch>
  • git push -f origin <new branch>

jinja line break


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