The Odyssey of Code

Today I learned that sh and bash are not the same thing. I'd been using sh bashfile.sh to run my bash scripts on the command line, and they have usually worked. When rewriting some grading scripts in my virtual Ubuntu environment, I ran into some syntax errors that I had not encountered on Mac.

Syntax error near "(" meant, in this case, that sh did not have the same syntax for arrays that bash did. My script had valid Bash syntax that was tripping up because my command asked sh to run it. Source

This helped me out a lot today - now I can update users.

Before, I had an embarrassing, silly bug caused by nesting an INSERT query inside a DELETE. The result was that the userId would change when I updated the user’s info (a big NOPE), and when I updated my admin user’s information, they were automatically re-added as a regular (non-admin) user.

This very helpful blog post details how to change character encoding from utf-8 to the more expansive utf8mb4.

Implications: * Eliminates one possible source of security vulnerabilities. When MySQL encounters a character outside of its default charset, it may respond by truncating the data, which leaves it open to injections. * Equally as important: now your database won't trip up over emoji.

Problem: Your syntax for adding or defining a column in MySQL is correct, but it causes a syntax error anyway.

Once you have installed and configured AWS CLI, then you can use a few handy commands to display information about various parts of your AWS architecture.

Assuming you just have 1-2 instances running, this is a good start. (Make sure to use the correct region.)

aws ec2 describe-instances --output table --region us-west-2

Once you have found the instance you need more details about:

aws ec2 describe-instances --output table --instance-ids <i-alphanumericinstanceidhere>

Open up a new Terminal tab and get the security group info as well: aws ec2 describe-security-groups --output table --group-names my-sg

To log in locally,

mysql -u root -p

Then you'll be prompted for your password.

To exit, \q, then it will tell you, "Bye"

When you get in,

show databases;

use ;

show tables;

create table ( , );

Only if you're sure you want to delete it:

drop table ;

To see the table:

select * from ;

Connect to your MySQL RDS instance on AWS

mysql -h myinstance.123456789012.us-east-1.rds.amazonaws.com -P 3306 -u mymasteruser -p

The endpoint of your instance in this example is:

myinstance.123456789012.us-east-1.rds.amazonaws.com

This didn't work for me, but it's worth trying again:

To upload a file to your EC2 instance, you will need:

the public DNS name of the instance

the absolute path to your key pair (.pem) file

the absolute path to the file you want to upload.

scp -i /path/my-key-pair.pem /path/SampleFile.txt [email protected]:~

The public DNS name of the EC2 instance in this example is:

ec2-198-51-100-1.compute-1.amazonaws.com

It's easier to do this with a lot of files if you archive the files locally first, upload the .tar file to your ec2 instance, then unarchive the .tar file there.

More details

Create an archive called "files.tar" that includes "a.txt" and "b.txt":

tar -czvf files.tar a.txt b.txt

You could also archive a child directory with its contents.

tar -czvf files.tar a_dir

You could archive everything in the current directory.

tar -czvf files.tar .

The "v" executes the command verbosely. Sometimes, when you're starting out, it's nice to see results. Without that, it "looks like nothing happened" but you can always check with ls and you should see your tar file there.

Unarchive the tar file with this:

tar -xzf files.tar

Successful test result looks like this

Failed test result will show this over and over until you manually stop it (Ctrl-C)

To run Artillery, provide the name of your test script file, i.e. test1.json or test1.yml

artillery run test1filename

Once your files are uploaded to your EC2 instance, and you have SSH-ed into it, you can run Artillery from your local machine,* given that your test script has the correct target specified.

The target for your EC2 instance looks like this:

"xx.xxx.xxx.xxx:yyyy" where the x's are the public IP address of your instance, and the y's are the port number that you have specified your app to listen to.

Don't forget to define a custom TCP rule in the security group for that specific port number. (Not sure if this is a recommended practice or a hacky fix.)

Once logged into the EC2 instance, do the following commands:

Install the nvm (node version manager).

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.32.0/install.sh | bash

Activate nvm.

. ~/.nvm/nvm.sh

Use nvm to install your desired version of node. (For simplicity, use the same version that you're using on your local machine. Check with node -v

nvm install 7.4.0

Confirm your installation of node.

node -e "console.log('Running Node.js ' + process.version)"

will output "Running Node.js v7.4.0" if the installation was successful.

Use the node package manager to install Express globally (or leave out the -g flag for a local installation).

npm install -g express

Successful installation looks like this: Express on your EC2 Instance

Arrays have length as an attribute, so you can call 'array.length'

StringObject.length()

Adjust your expectations of yourself, because the last math class you took is probably a few years further behind you than it is for your classmates. "Comparison is the thief of joy."

Fill in the gaps as needed with some good MOOCs. It's OK to watch dumb stuff on YouTube, as long as you switch to online lectures at some point. Don't underestimate the value of even passively absorbing the information as you clean your house, or something. Hearing a tough concept explained several different ways will help you understand it.

A subpar grade indicates a lack of understanding the topic covered, well enough to apply it. It can be a sign that you must spend more time on this concept, and/or change your approach to studying for the class. You are not the only one who is afraid you're not smart enough to get it.

Due to the overwhelming number of different learning resources available online, anyone who wants to start learning how to code can easily fall into the trap of trying to figure out the best way to learn, big-picture. I spent at least 2 months researching various bootcamp / MOOC options, and during that time my coding skills did not actually improve, because I wasn’t writing any code.

Although people mean well, they will offer you a hundred dissenting opinions about the best ways to learn, and the best languages / frameworks to start with. If you tried to listen to them all, you’d end up knowing how to write “Hello, world!” in every language, and maybe not much more.

Just say, “Thanks for the suggestion! I’ll look into that / save it.” It makes them feel good, and maybe you will get around to it eventually, but continue your focus on building something that you like.

grep, ack, and ag are searching libraries that are used to search files for things like variable names.

The one you use is a matter of personal taste. 

ack and ag must be installed.  grep is more commonly used, especially in the absence of the first two, so you have to know it.  however, ack and ag are both faster than grep, and they support more modern APIs. 

ag has version control system (VCS) awareness.  

Conquering the Command Line by Mark Bates.  (Chapters 2 and 5)

In PEMDAS, the modulus is at the same hierarchical level in the order of operations as multiplication.