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Today I Learned

A part of my day to day learning

6 min read

Here is my journey so far:

Fri Aug 17 14:28:36 +0545 2018

How to stash untracked files in git?

git stash -u stash the untracked files in git without adding files to staging area New versions of git now have git stash --all which stashes all files, including untracked and ignored files. git stash --include-untracked no longer touches ignored files

Mon Aug 13 09:28:52 +0545 2018

What is the difference between json.dump() and json.dumps() in

python?

json.dump takes file stream and will dump into a file stream while json.dumps takes string argument and often used for printing parsing etc. json.dumps == dump string :D

Thu Aug 9 2018

Wrote a blog and a script to Organize Desktop and group similar files in a Directory

echo '\n#### ' `date` appends UNIX commands date to string in shell

How to check if a string endswith any of the elements from a list in python?

such list of string must be tuple for that purpose


>>> photos_extension = ("jpg", "JPEG", "jpeg","png","HEIC","svg","JPG")
>>> file_name = "picofNepal.jpg"
>>> file_name.endswith(photos_extension)
True

Wed Jul 18 2018

How to fix nginx HSTS error?

I fixed by updating the certificate

Mon Jul 16 2018

Built the script and alias it to .zshrc for daily logging

How to open nano at the end of the file?

nano +9999 opens the file at end of file

about:about opens custom url in both the browser in firefox and chrome

Tue Oct 2 13:54:14 +0545 2018

How to redirect to https from http using Flask url_for() ?

Since Flask url_for does not respect http or https while redirecting, always use redirect(url_for('func_name', _external=True)) to respect the root URL and Scheme(http or https) Used

Wed Oct 3 17:01:09 +0545 2018

How to remotely execute remote bash script in remote machine from local machine?

To remotely execute a script residing in remote machine, do this:

ssh username@host.address './remotescript.sh'

On doing so remote script is executed however node module are not found and executed hence to execute the npm tools like pm2 follow the following steps:

  1. Type the following commands in your remote machine:” echo $PATH” It will output results like below: “/home/ubuntu/bin:/home/ubuntu/.local/bin:/home/ubuntu/.nvm/versions/node/v8.9.4/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/sn$”

  2. Copy the above output and open the file with texteditor like nano remotescript.sh and add the new line at the start of file. The new line must be like : “export PATH='{step 1 Output}'” remember that the {step 1 Output} looks like this /home/ubuntu/bin:/home/ubuntu/.local/bin:/home/ubuntu/.nvm/versions/node/v8.9.4/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin$

  3. Now save and close the file and execute your remote file like below:

    ssh username@host.address './remotescript.sh'

CONGRATS!!!, You just ran your remote script in remote machine from local machine: let me know if any problem occurs :)

Wed Oct 3 17:01:09 +0545 2018

How to find the length of a set in javascript?

Use set_variable.size like below:

var setTempVariable = new Set([1,2,3,4])
console.log(setTempVariable.size) // Outputs 4

Tue Oct 23 17:02:53 +0545 2018

How to use or operator in regex to match either group?

I had a use case to match either a number or a fixed string which I did by using following regex:

  `((^[0-9]+$)|FIXED$)`

Using + and $ helped me to exact match either of the group i.e number or ‘FIXED’ string. + looks for 0 or 1 repetition while $ matched the end of string

Sun Feb 3 23:59:31 +0545 2019

Simple Mail server for debugging in python

python -m smtpd -c DebuggingServer -n <source_address>:<port>

If default mailserver will be enable in port localhost:8025, Anything sent to this address and port will be sent in STDOUT

Happy Email debugging Folks:

telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 Shivas-Macbook.local Python SMTP proxy version 0.2
helo localhost #To connect
250 Shivas-Macbook.local
mail from: username@mymail.com # From
250 Ok
rcpt to: shivaji@@mymail.com #receipent
250 Ok
data #data to send message
354 End data with <CR><LF>.<CR><LF>
Subject: Hello
Hello,
This is sample test
Me
.

End telnet with a . at the end

In STDOUT after sending message from telnet :

python -m smtpd -c DebuggingServer -n

---------- MESSAGE FOLLOWS ----------
Subject: Hello
Hello,
This is sample test
Me
------------ END MESSAGE ------------

Thu May 16 10:32:44 +0545 2019

How to create wheel from setup.py?

run python setup.py wheel inside the package root

Download wheel or source from pip Python packages

pip download -r requirements.txt --prefer-binary to download whl file. ` pip download -r requirements.txt –no-binary :all: to download source file, .gz or .zip`

Wed Aug 28 09:28:39 +0545 2019

How to exclude files and folders when compressing using tar?

Use --exclude as many times you like to exclude files and folders.

 cd <directory> #DIrectory in which you want to compress the files and folders
 tar --exclude='./node_modules' --exclude='.excluding_folder_name' --exclude='./test.py' --exclude='./env' -czvf excluded.tar.gz .

Mon Nov 11 16:49:56 +0545 2019

Removing Sensitive information from git

  git filter-branch --force --index-filter \
  "git rm --cached --ignore-unmatch -r <FILE_NAME_OR_FOLDER_IF_FOLDER_-r_AS_ARGS>" --prune-empty --tag-name-filter cat -- --all

This will Force Git to process, but not check out, the entire history of every branch and tag, Remove the specified file, as well as any empty commits generated as a result, Add file or folder to .gitignore once removed to ensure you won’t commit again

Wed Jan 22 13:26:47 +0545 2020

Solve CORS issue in Flask API call

Do this in your response @app.after_request decorator

@app.after_request
def add_headers(response):
    white_list_url= ['https://yourserverorigin.com/','http://localhost:8000'] #List of URLs you want to allow
    if request.headers['Origin'] in white_list_url:
        response.headers.add('Content-Type', 'application/json')
        response.headers.add('Access-Control-Allow-Origin', request.headers['Origin'] )
        response.headers.add('Access-Control-Allow-Methods', 'GET')
        response.headers.add('Access-Control-Allow-Headers', 'Content-Type,Authorization')
        response.headers.add('Access-Control-Expose-Headers', 'Content-Type,Content-Length,Authorization,X-Pagination')
    return response

Thu Dec 10 14:22:04 +0545 2020

To take mongodump with timestamp:

mongodump --db <db_name> -o dump_`date "+%Y-%m-%dT%H:%M:%S%Z"`

remember the backtick at start of “date” after dump and at the end

Thu Dec 10 14:22:04 +0545 2020

Collection Specific mongorestore command

mongorestore --db <db_name> --collection <collection_name> <dump_location>/<collection_name.bson>

to restore all: Mongorestore

mongorestore <dump_location>

Sat Feb 5 03:45:39 +0545 2022

Learn ways to initialize vector in Rust

  1. Using vec! macro

  2. Using new()

     let mut vec = Vec::new();

  3. Using with_capacity

     let mut vec = Vec::with_capacity(10);

  4. To sort vector using sort_unstable it uses https://github.com/orlp/pdqsort and this https://doc.rust-lang.org/std/vec/struct.Vec.html#method.sort_unstable

     let mut nums = vec![-1,-5,-3,1,2,-1];
 nums.sort_unstable();

Tue Feb 8 23:28:16 +0545 2022

Rust: Declaring constant

    For constant declaration one must include `Data Types` and `const` doesn't allow to use `mut`. 

  ```rust
  const NUM:u8 =8;
  ````

Thu Feb 17 13:21:02 +0545 2022

Rust: Array slice

For slicing an array use type signature &[T]

   #[test]
    fn slice_out_of_array() {
        let a = [1, 2, 3, 4, 5];

        let nice_slice = &a[1..4];

        assert_eq!([2, 3, 4], nice_slice)
        
        }

Tuple indexing in rust access a tuple element directly by using a period (.) followed by the index of the value to access.

  let numbers = (1, 2, 3);
  let second = numbers.1 ; //2

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