make it possible to resize pdf in linux

 See more details here https://r4ven.fr/en/blog/ubuntu-compress-pdf-nautilus/

updating fonts in ubuntu

To bulk install fonts in Ubuntu, copy font files (.ttf, .otf) to ~/.local/share/fonts/ (for your user) or /usr/share/fonts/ (system-wide), then run fc-cache -fv in the terminal to update the font cache, or use the graphical Font Manager by dragging and dropping them in. 

non-blocking network calls when using asyncio in python

To avoid blocking your Event Look in Python when using asyncio, do not use `requests` but use `aiohttp`

Here is some example code. `aiohttp` gives us a session that works well on the asyncio Event Loop.

import aiohttp
import asyncio

async def fetch_real_url(session, url):
    async with session.get(url) as response:
        return await response.text()

async def main():
    async with aiohttp.ClientSession() as session:
        urls = ['http://python.org', 'http://google.com', 'http://example.com']
        
        # Create a list of tasks
        tasks = [fetch_real_url(session, url) for url in urls]
        
        # Run them all at once
        responses = await asyncio.gather(*tasks)
        
        print(f"Downloaded {len(responses)} pages concurrently.")

if __name__ == "__main__":
    asyncio.run(main())

Other useful things...

• `async` returns a coroutine object that can be scheduled.
• Calling this function returns a `future` — a placeholder for a result that hasn't happened yet. It tracks the state (Pending, Finished, Cancelled).
• The Event Loop is single-threaded. The Event Loop serves as a scheduler of these tasks.

Using python 3 on mac

 Read more here https://opensource.com/article/19/5/python-3-default-mac

SSH returns: no matching host key type found. Their offer: ssh-dss

 Fix is

ssh -oHostKeyAlgorithms=+ssh-dss root@192.168.8.109

Read more here https://askubuntu.com/questions/836048/ssh-returns-no-matching-host-key-type-found-their-offer-ssh-dss 

format decimal and doubles in Java to desired decimal places

 To format numbers in java, simple

String.format("%.2f", 132.2372342)

Free up space in ubuntu server

 Clean old kernels

• Check for kernet is use : uname –r
• Check for old kernels : dpkg --get-selections | grep linux-image
• Remove unused kernels : dpkg --get-selections | grep linux-image

Clean APT (Pulled from https://askubuntu.com/questions/5980/how-do-i-free-up-disk-space)

• To delete downloaded packages (.deb) already installed (and no longer needed)
• sudo apt-get clean
• To remove all stored archives in your cache for packages that can not be downloaded anymore (thus packages that are no longer in the repository or that have a newer version in the repository).
• sudo apt-get autoclean
• To remove unnecessary packages (After uninstalling an app there could be packages you don't need anymore)
• sudo apt-get autoremove

Finally, Check Disk Space

• df -h /

view largest installed debian packages on unix

More details on this link https://www.commandlinefu.com/commands/view/3842/list-your-largest-installed-packages-on-debianubuntu

dpkg-query -Wf '${Installed-Size}\t${Package}\n' | sort -n | tail -n 10

See more details here https://linoxide.com/show-installed-package-size-ubuntu-debian/

pull multiple files from android via adb

Got answer from https://stackoverflow.com/questions/11074671/adb-pull-multiple-files

adb shell 'ls /sdcard/DCIM/Camera/20200327*.mp4' | tr -d '\r' | xargs -n1 adb pull

get the size of folder contents

du -sh 

Output

15M big_folder
0 dead.letter
4.0K some_file
4.0K some_other_file

challenges with grails unique: true

Grails does not evaluate a unique constraint at GORM level but at the database level

    static constraints = {
        property unique: true
    }

This means that you would not get a grails.validation.ValidationException but a org.springframework.dao.DataIntegrityViolationException.

This means that

domainInstance.validate()

would not capture a duplicate "property"

Sometimes cron runs twice

I suspected cron was running twice. I confirmed by checking the system logs

grep CRON /var/log/syslog

Then I killed cron and restarted it

sudo /etc/init.d/cron stop
sudo /etc/init.d/cron start

Tail vs Less

Learnt a good chunk about less and tail from this site http://www.brianstorti.com/stop-using-tail/ 

Access child components in vue.js

Sending mail in unix with attachment

You would need to install sharutils

sudo apt-get install sharutils

Then run this

uuencode <path_to_file> <name_to_give_attachment> | mail -s "Subject" foo@example.com

Also see http://soamweird.blogspot.com/2016/03/sending-mail-in-unix.html

Sorting by type first then alphabetically

The script below ensures that items are sorted by type first then by alphabetical order.

The spaceship operator

Just ran into this and I thought it was really cool.

So the spaceship operator (<=>) delegates to the compareTo method:

assert (1 <=> 1) == 0
assert (1 <=> 2) == -1
assert (2 <=> 1) == 1
assert ('a' <=> 'z') == -1

For more checkout http://groovy-lang.org/operators.html

Sending mail in unix

When sending an email from unix do the following

echo "Mail Message" | mail -s "Subject" person@home.com

In order to avoid getting your email marked as spam, ensure that the sending email is something realistic, probably a domain you own i.e. awesome@homelypeople.com

Reset local git branch to match remote

Setting your branch to exactly match the remote branch can be done in two steps:

git fetch origin
git reset --hard origin/master

Deleting git tags

Delete tag locally

git tag -d tagName

Delete tag on remote

git push --delete origin tagName