TIL

• Bash
• Docker
• Node
  • npm
  • nx
• Git
• SQL
• Python And Jupyter

Ubuntu (or more generally Linux)

• Checking the current linux kernel version: uname -r
• Checking out which distribution and version of linux you're running: cat /etc/issue
• Running a program with some namespaces unshared from parent: unshare [options] (check options here)

Bash

• Removing a directory and its contents: rm -rf [dirname]
• Moving a directory and its contents: mv source/ target/
• Copying a directory and its contents: cp -r source/ target/
• To rename a single file just use mv!
• Printing a message to the console: echo “[my message]”
• Writing to a text file: echo “[my message]” > [my .txt file]
• Printing a file line by line: cat [file] | more
• Printing the first few lines of a file: head [file] or head [file] -n [number of lines]
• Writing stdout and stderr outputs to a file: [command that generates output] &> [filename.txt]
• finding files by name in the current directory: find . -name [filename]
• finding files by name in a directory, with depth: find [directory] -name [filename]
• finding files by name in a directory: find [directory] -maxdepth [depth] -name [*filename*] -print
• searching files for a string or regex: grep '[regex]' [directory] -rnw
• searching files for a string (additional options): grep '[regex]' [directory] -rnw -A [# of lines to show before match] -B [# of line after]
• Display shared dependencies of a binary: ldd [binary]
• Running a command (or interactive shell) with a special root directory: chroot [new root] [command]

scripts

• Printing a variable: echo "$variable"
• Storing the output of a command in a variable : variable="$(command)"
• Parsing JSON with bash: check the jq tool https://stedolan.github.io/jq/ !

processes

• Listing all running processes: ps aux
• Listing open node files and their processes: lsof -i | grep node
• Searching for a process that matches a string: ps aux | grep [search string]
• Killing a process: kill [process ID]
• Killing all processes which match a name: pkill [name]
• Getting the name of the command that created a process: ps -o comm= -p [PID]
• Getting some info on a process: ps -Flww -p [PID]

Node

npm

• Checking which version of npm is running: npm -v
• Going back to a previous version of npm (for example npm 5): npm install -g npm@5
• Listing all globally installed modules: npm ls -g --depth 0

nx

• Generating dependency graph: yarn nx dep-graph

nvm

• Listing installed Node versions: nvm ls
• Using one of the installed Node versions: nvm use [version]
• Updating and managing multiple versions of Node: check https://github.com/creationix/nvm

Paths and Dirs

• Getting the path of the current directory: const DIR_PATH = path.resolve(__dirname);
• Going from a relative to an absolute path: path.resolve(DIR_PATH, '../../relative/path')

Git

• Comparing the last two commits: git diff HEAD^ HEAD
• Comparing the last two commits and only showing changed filenames: git diff HEAD^ HEAD --name-only
• Comparing the last commit with the staged differences: git diff --cached
• Limiting the diff to one file: git diff HEAD^ HEAD -- [filename]
• Specifying the number of lines to show around each diff: git diff HEAD^ HEAD -U[# of lines]
• Ignoring a file (like package-lock.json) from a git diff: git diff HEAD^ HEAD -- . ":(exclude)package-lock.json"
• Reverting a single file to the last commit: git checkout [filename]
• Fetch + rebase: git fetch --all && git rebase -v
• Adding a remote origin: git remote add origin [url]
• Listing all branches: git branch -r
• Listing all branches starting with the ones with the most recent commits: git branch --sort=-committerdate
• Deleting a branch locally: git branch -d [branch]
• Removing a remote branch (be careful!!): git push origin --delete [branch]
• Copying the content of a branch to a new one: git checkout -b new_branch old_branch
• Going back to head while saving local modifications: git stash
• Undoing a git stash with: git stash pop
• Merging two branches: git checkout the branch you want to merge to, then git merge [branch to copy from]
• Undoing the last commit ONLY if not pushed yet. Your changes will still be kept in the filesystem: git reset HEAD@{1}
• Untracking a file that has already been commited, after adding it to .gitignore: git rm --cached [filename]
• Undoing a delete when you haven't yet commited: git reset --hard HEAD^

Docker

• Displaying system-wide info: docker info
• Displaying docker version: docker -v
• Getting docs on a command (including options): docker [command] --help
• Checking which images you have locally: docker images
• Pulling an image (or a repository) from a registry: docker pull [name]
• Running a docker image in interactive mode: docker run --interactive --tty [image name] or docker run -it [image name] sh
• Running a docker image: docker run [image ID]
• Deleting a docker image: docker image rm [name]
• Checking how a docker image has changed over time: docker history [image id]
• List running containers: docker ps
• Dumping some info on a particular image (created at, ENV variables, etc...): docker inspect [container ID or image ID]
• Pausing all processes in a container: docker pause [container ID]
• Unpausing the processes in a container: docker unpause [container ID]
• Killing a container: docker kill [container ID]
• Executing a command on a running container: docker exec [container ID] [command, like "ps aux"]
• Checking the logs of a running container: docker logs [container ID]

PostgreSQL

• Checking which version is running: postgres -V
• Launching the postgresql CLI: psql

The following commands should all be typed inside the PostgreSQL server:

• Listing the defined databases on the server: \l

SQL

Selection

Here is the format of a select statement: SELECT column or columns FROM tablename WHERE optional conditions

• selecting all columns of all rows of a table: SELECT * from [tablename]
• selecting all columns of all rows where [column] starts with some [characters]: SELECT * from [tablename] WHERE [column] LIKE '[characters]%'
• selecting all columns of all rows where [column] contains some [characters]: SELECT * from [tablename] WHERE [column] LIKE '%[characters]%'
• selecting all columns of all rows where [column] ends with some [characters]: SELECT * from [tablename] WHERE [column] LIKE '%[characters]'
• Other conditional selections in SQL:
  • = Equal
  • > Greater than
  • < Less than
  • >= Greater than or equal
  • <= Less than or equal
  • <> Not equal to

Creating tables

Here is the format of a create statement:

create table [tablename]
(
 [column 1] [data type] [optional constraint],
 ....
)

Here are the most common Data types:

• char(size) : Fixed-length character string. Size is specified in parenthesis. Max 255 bytes.
• varchar(size) : Variable-length character string. Max size is specified in parenthesis.
• number(size) : Number value with a max number of column digits specified in parenthesis.
• date : Date value
• number(size,d) : Number value with a maximum number of digits of "size" total, with a maximum number of "d" digits to the right of the decimal.

Inserting

Here is the format of an insert statement:

insert into [tablename]
 (first_column, ... last_column)
 values (first_value, ... last_value);

Updating

Javascript Debugging

• Using console.group("Group name"), logging... and then console.groupEnd()
• A convenient way to print objects is console.dir(object, { depth: null })

Eslint

• Ignoring a rule in a file (for example max-lines): /* eslint max-lines: 1 */
• Ignoring an error in the next line: /* eslint-disable-next-line id-length */
• Disabling eslint for the whole file: /* eslint-disable */

AWS

AWS CLI

(PS: These commands are not guaranteed to be up to date, but I just put them here to find them easily

• Listing the ECS tasks of a cluster: aws ecs list-tasks --cluster [cluster]
• Describing an ECS task: aws ecs describe-tasks --cluster [cluster] --tasks [task ID or list of IDs separated by a space]

Python and Jupyter

Conda

If running a Jupyter Notebook, be sure to run the following commands from within the Jupyter terminal

• Checking Conda version: conda -V
• Updating Conda package: conda update [package]
• Checking the list of all Conda packages: conda list
• Upgrading Conda version: conda update conda and then conda update anaconda to update Anaconda packages
• Checking Mamba version: mamba -V
• Upgrading Mamba: mamba update -n base mamba

Jupyter

• Checking Jupyter version: jupyter notebook --version
• Upgrading Jupyter if using Anaconda: conda update jupyter