# Environment Variables and \`PATH\` Environment variables are settings Windows hands to every program, read and set in PowerShell with $env:, and PATH is the one that lists the folders searched for a command, which is why a program outside them is not recognized until you run it by its path or add its folder for this session. Apprentice · PowerShell · Updated November 10, 2026 ## After this lesson you can - Read and set an environment variable for this session with $env:, and tell it apart from a PowerShell variable - Fix a command that is not recognized by running it with its path, or by adding its folder to $env:PATH for this session ## Key takeaways - Environment variables are settings every program can read. `$env:USERNAME` reads one, and `$env:POWER = 'on'` sets one. - A plain `$POWER` stays inside PowerShell. Programs and scripts that read the environment see only `$env:POWER`. - PATH is the list of folders searched when you type a command's name. A command outside them is not recognized. - Run it by its path (`.kettle-bot.ps1`), or add its folder with `$env:PATH += ";"`, for this window only. You install a tool, following its guide step by step. You open PowerShell, type the tool's name, and get red text: *is not recognized as a name of a cmdlet, function, script file, or executable program*. Or the guide says "set the `JAVA_HOME` environment variable" as if you'd know how. People reinstall, restart, and give up over these two messages, and both are about the same thing: **environment variables**, the settings Windows hands to every program it starts. Developers set them up on every new computer, and help-desk techs fix them for other people every week. This lesson uses the workshop from *Variables: $name*. If you closed PowerShell since then, run that lesson's practice-folder lines again. ## Settings every program can read: \`$env:\` Your variables from the last lessons live inside PowerShell. Windows also keeps a set of its own, the environment, and gives a copy to every program it starts: your user name, your temporary folder, where programs are installed. Read one with `$env:` in front of its name, read "the environment's": ```powershell $env:USERNAME $env:TEMP Get-ChildItem Env:Program* ``` ```text Sam C:\Users\Sam\AppData\Local\Temp Name Value ---- ----- ProgramFiles(x86) C:\Program Files (x86) ProgramW6432 C:\Program Files ProgramData C:\ProgramData ProgramFiles C:\Program Files ``` `Env:` is a drive, like `C:`, that holds every environment variable, so `Get-ChildItem Env:` lists them all. On a Mac or Linux the names differ: `$env:USER` and `$env:HOME`. ## Setting one, for this window Ada's kettle-bot is a tiny script, and its one line reads the environment. Run a script in the folder you're in with `.\` in front of its name, read "this folder's": ```powershell Set-Location "$HOME\terminal-practice\workshop" Get-Content kettle-bot.ps1 .\kettle-bot.ps1 ``` ```text if ($env:POWER -eq "on") { "Pouring tea..." } else { "NO POWER" } NO POWER ``` A plain variable called `POWER` won't do: it's PowerShell's own box, and the kettle-bot looks in the environment. Setting `$env:POWER` puts it there: ```powershell $POWER = 'on' .\kettle-bot.ps1 $env:POWER = 'on' .\kettle-bot.ps1 cmd /c "echo POWER is %POWER%" ``` ```text NO POWER Pouring tea... POWER is on ``` The last line asks a different program, Windows' old Command Prompt (`cmd`), and it sees `POWER` too: every program started from this window gets a copy. A setting made this way lasts until you close the window. `Remove-Item Env:POWER` takes it away sooner. In Windows PowerShell 5.1, scripts don't run at first, so `.\kettle-bot.ps1` stops with an error; *Why a Script Won't Run: The Execution Policy*, in the next chapter, explains why. On a Mac or Linux, `sh -c 'echo POWER is $POWER'` stands in for `cmd`. ## PATH: where PowerShell looks for commands When you type a name, PowerShell checks its own commands, then searches a list of folders for a program or script with that name. The list is the environment variable `PATH`, with a `;` between folders. `-split ';'` shows it one folder a line: ```powershell $env:PATH -split ';' ``` ```text C:\Program Files\PowerShell\7 C:\Windows\system32 C:\Windows C:\Windows\System32\Wbem C:\Windows\System32\WindowsPowerShell\v1.0\ C:\Windows\System32\OpenSSH\ C:\Program Files\PowerShell\7\ C:\Users\Sam\AppData\Local\Microsoft\WindowsApps ``` Yours is longer: every installer that adds a folder makes it longer. PowerShell 7 puts its own folder first each time it starts. Ada's oil can lives in `tools`, which isn't on the list: ```powershell oil gears ``` ```text oil: The term 'oil' is not recognized as a name of a cmdlet, function, script file, or executable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again. ``` ![PowerShell looking for oil: it searches the PATH folders in order, C:\Program Files\PowerShell\7, C:\Windows\system32, C:\Windows and the rest, finds no oil, and answers not recognized; with the workshop's tools folder added to the end of the list, the same search finds oil.ps1](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/f14cfabb00024dc7ad5c45ae3434738e.webp) That's the whole meaning of "is not recognized": no command by that name, and no file by that name in any PATH folder. A typo gives it, and so does a program installed into a folder that isn't on the list. PowerShell doesn't even look in the folder you're in, so typing `kettle-bot` in the workshop gives the same error. That's why the kettle-bot needed `.\`. ## Two fixes, for this window Give the path, and PowerShell doesn't need to search. Or add the folder to `PATH`, and the short name works from anywhere. `+=` adds to the end, keeping every folder already there, and the text starts with `;` to separate it from the last one: ```powershell .\tools\oil.ps1 gears $env:PATH += ";$HOME\terminal-practice\workshop\tools" oil gears (Get-Command oil).Source ``` ```text Glug, glug. The gears are oiled and shining. Glug, glug. The gears are oiled and shining. C:\Users\Sam\terminal-practice\workshop\tools\oil.ps1 ``` `Get-Command` says where a name was found. Close the window, and `PATH` is back to what it was. On a Mac or Linux the separator is `:`, and the name must be written `$env:PATH`, in capitals. Installers change `PATH` for good, for every new window, and an install guide may show a line like this one. You don't need to run it: this course keeps every change for the window you're in. Get it wrong, and every new window loses commands. ```powershell [Environment]::SetEnvironmentVariable('Path', [Environment]::GetEnvironmentVariable('Path', 'User') + ";$HOME\tools", 'User') ``` The mouse way is Windows' *Edit environment variables for your account* window: search Start for "environment variables". A change made either way reaches only windows opened afterward. ## Try it in the terminal [Terminal Quest: The Clockwork Workshop, goals 3 to 4](https://www.ask-codey.com/games/terminal-quest/workshop/powershell/step): played right on the lesson page. You're Ada's apprentice, and her workshop is at `$HOME\workshop`. Give the kettle-bot POWER with an environment variable and run it with `.\kettle-bot.ps1`, then put the tools folder on your PATH and oil the gears. ## Check yourself 2 questions to try on the lesson page. ## So what "Is not recognized" isn't a mystery anymore: the name isn't a command, and its file isn't in a PATH folder. Give the path, or add the folder, and the settings every program reads are yours to see and set. ## Key terms - [$env:](https://www.ask-codey.com/glossary/env) - [Environment Variable](https://www.ask-codey.com/glossary/environment-variable-operating-system) - [PATH](https://www.ask-codey.com/glossary/path-operating-system) ## Cheat sheets - [Environment Variables and \`PATH\`](https://www.ask-codey.com/cheat-sheets/powershell-environment-variables-cheat-sheet) ## Related - [Variables: \`$name\`](https://www.ask-codey.com/lessons/powershell-variables) - [Why a Script Won't Run: The Execution Policy](https://www.ask-codey.com/lessons/powershell-execution-policy) - [Exercise: The Workshop's Machines](https://www.ask-codey.com/lessons/exercise-powershell-the-workshops-machines) Source: https://www.ask-codey.com/lessons/powershell-environment-variables