While I have been using Linux for over 2 years now, frankly I had never thought about automating tasks using simple bash scripts. This means that while I did not know about bash scripting from a syntactical point of view, I was very comfortable using the command line and it’s various commands.

And so my journey misadventures with bash scripting started with an idea, as always.

1) Idea!⌗

Need to switch to light theme on vim…wait! Do I manually edit my config file every time? Time to write my first bash script.

2) Overview⌗

I needed to start from the basics. Web search + Reddit later I landed on a website ‘learn-x-in-y-minutes’. 4 hrs to understand basic syntax while executing some code snippets.

3) Implementation?⌗

Fundamentally, the script would have to edit the vimrc file –

set background=dark → set background=light

sed command for the rewriting job. I opened up the man page on date command and found that using format specifiers returned time in integer.

CURRENT_TIME=$(date +%H%M%S)
if [ "$CURRENT_TIME" -gt "$STARTING_TIME" ] && [ "$CURRENT_TIME" -lt "$END_TIME" ]
then
  sed -i "s/set\\ background=$LIGHT_THEME/set\\ background=$DARK_THEME/" ~/.vimrc
else
  sed -i "s/set\\ background=$DARK_THEME/set\\ background=$LIGHT_THEME/" ~/.vimrc
fi

Debugging! END_TIME less than STARTING_TIME. A swap function should account for that.

4) Issues!⌗

Why is a file with name ‘180000’ created every time I execute the script? And why is my downloads folder so cluttered? Need a file organizing script…

5) One day and awk later⌗

Need a list of extensions in a directory. Kind stranger on StackOverflow, how do I understand this insane syntax?

find . -type f | awk -F. '!a[$NF]++{print $NF}’

WHAT IS AWK? Okay, just need to go through the GNU manual…arrays in awk are super WEIRD! How about I usesort…

find . -maxdepth 1 -type f  |  awk -F . '{print $NF}' |  sort -u

My own solution that I UNDERSTAND! mv+ regex should finish the work.

6) Send 100MB file over Facebook?⌗

Honestly, I could have provided a drive link and be done. But something in me got excited over somehow bypassing the upload limit of 25 MB. Time to work.

7) Split it!⌗

In a GitHub repository I found the usage of split - so, I CAN SPLIT FILES into pieces without losing data. Recombination? cat command to the rescue. I love Unix forums.

split --bytes=$CHUNK_SIZE --additional-suffix=$SPLIT_FILE_EXTENSION -d $FILENAME $PREFIX

8) JUST ENCRYPT IT!⌗

It would be useful if I could implement something from Cryptography I course on Coursera that I took. In a sense, I’d learn two things simultaneously. Referred YouTube on openssl, went through the man page and added in some flags of my own:

openssl enc -aes-256-cbc -base64 -pbkdf2 -iter 100000 -pass pass:$PASSWORD -in $file -out fenc/$file

9) Finally…?⌗

IT WORKED! 100 MB pdf sent over Facebook, in chunks of 24 MB, with the decryption working on the other end just as I wanted!

Wait, why are files of name ‘180000’ scattered around my storage? Oh no, forgot to turn off the buggy script…

References:⌗