Terminal Survival Kit · System Design Notes

00 /What a terminal is

In plain words

A terminal is a window where you type commands instead of clicking. The terminal always works "inside" one folder, the current folder. Commands that use files look there first.

Open one: on Windows search for PowerShell (or Git Bash if you installed Git). On a Mac open Terminal. On Linux, the keyboard shortcut is usually Ctrl+Alt+T.

01 /Moving around and looking at files

You want to	Bash (Mac, Linux, Git Bash)	PowerShell (Windows)
Where am I?	`pwd`	`Get-Location` (or `pwd`)
List files	`ls`	`dir` (or `ls`)
Go into a folder	`cd lab-folder`	`cd lab-folder`
Go up one folder	`cd ..`	`cd ..`
Make a folder	`mkdir mylab`	`mkdir mylab`
Show a file	`cat file.txt`	`type file.txt` (or `cat`)
Copy, move, delete a file	`cp a b`, `mv a b`, `rm a`	`Copy-Item a b`, `Move-Item a b`, `Remove-Item a`
Delete a folder and everything in it	`rm -rf folder`	`Remove-Item -Recurse -Force folder`

Careful with delete

There is no recycle bin. rm -rf and Remove-Item -Recurse -Force delete for good, and the folder name must be exactly right.

02 /Starting a lab

Which terminal are you using?

mkdir my-lab && cd my-lab
unzip ~/Downloads/my-lab.zip
ls

mkdir my-lab; cd my-lab
Expand-Archive -Path "$HOME/Downloads/my-lab.zip" -DestinationPath .
dir

Unzip every lab into its own new folder, then run all commands from inside that folder. Many "file not found" errors are only "I am in the wrong folder".

03 /Running scripts

You want to	Bash	PowerShell
Run a script in this folder	`./test.sh`	`.\test.ps1`
Run Python	`python3 file.py`	`python file.py` (or `py file.py`)
Stop a running command	Ctrl+C	Ctrl+C
Repeat the last command	Up arrow, Enter	Up arrow, Enter
Clear the screen	`clear`	`cls`

If PowerShell refuses to run a .ps1 file, run it like this once: powershell -ExecutionPolicy Bypass -File .\test.ps1.

04 /Pipes, searching and saving output

You want to	Bash	PowerShell
Send the output of one command into another (a pipe)	`docker ps \| grep web`	`docker ps \| Select-String web`
Search a file for text	`grep error app.log`	`Select-String error app.log`
Show the first or last lines	`head -20 f`, `tail -20 f`	`Get-Content f -TotalCount 20`, `Get-Content f -Tail 20`
Save output to a file	`docker compose logs > logs.txt`	`docker compose logs > logs.txt`
Count lines	`wc -l file`	`(Get-Content file).Count`

05 /Environment variables

You want to	Bash	PowerShell
Set one for the current terminal	`export REDIS_HOST=cache`	`$env:REDIS_HOST = "cache"`
Set one for a single command	`REDIS_HOST=cache docker compose up -d`	`$env:REDIS_HOST = "cache"; docker compose up -d; Remove-Item Env:REDIS_HOST`
Read one	`echo $REDIS_HOST`	`echo $env:REDIS_HOST`

06 /Quotes and long lines

Bash: single quotes '...' keep the text exactly as typed. Double quotes "..." allow $variables.
PowerShell: the same idea, but when you pass JSON with double quotes to a program such as curl.exe, put a backslash before each inner quote: -d '{\"name\":\"asha\"}'.
Long lines: end the line with a backslash in Bash, and with a backtick in PowerShell, then continue on the next line.

07 /Three Windows traps

curl in PowerShell is a different command. Type curl.exe.
python3 on Windows may open the Microsoft Store. Use python or py.
In Git Bash, a path like /app inside a command can be rewritten to C:/Program Files/Git/app. Put MSYS_NO_PATHCONV=1 in front of the command, or use PowerShell.

More fixes are in the Windows Troubleshooting guide.