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yarn command not found after installing via npm

As per the yarn installation for yarn v2, they want you to install using npm install -g yarn. So I ran sudo npm install -g yarn on Ubuntu 20.04. But after I do that, it says command not found.
❯ sudo npm install -g yarn
> yarn#1.22.10 preinstall /usr/local/lib/node_modules/yarn
> :; (node ./preinstall.js > /dev/null 2>&1 || true)
❯ yarn --version
zsh: command not found: yarn

sudo npm install -g npm
then
sudo npm install -g yarn
Then reboot your system. That did it for me.
Before a reboot only sudo yarn worked. I tried looking at file permissions but everything seemed in order and the files were executable as expected. Nevertheless after a reboot it worked.
If you go to /usr/local/bin after the installation there's a link there to where yarn.js lives, as expected, and file permissions for it were also correct.
/usr/local/bin is added to $PATH, so it's surprising that it doesn't see the new cmd right away, but perhaps it didn't reload or map it until after the reboot? I don't know. But I just spent a good hour trying to figure this out so I'm posting what worked for me to spare other the hassle.

TL;DR
If you are managing node via nvm, then probably the path to yarn binary is not included in the $PATH variable. You should add this -
# Add this at the end (or after the $NVM_DIR initialization)
# in your profile - .bashrc | .zshrc | .profile, etc
export PATH="`yarn global bin`:$PATH"
at the end of your profile file (.zshrc for me) or at least after the $NVM_DIR initialization.
I have recently faced this issue and while searching for a solution, I landed up here.
Here is what my environment looks like:
OS: Ubuntu 20.04
Shell: zsh
NodeJS: managing it via nvm, and NOT apt.
After going through all the answers, I was not keen on uninstalling anything. So I tried to dig a bit deeper.
I installed yarn via npm install -g yarn command. So the first thing I wanted to verify was the location of the yarn binary. To do this, I ran the command where yarn which lists the installation path for the yarn binary.
$ where yarn
/home/<user_name>/.nvm/versions/node/v16.11.1/bin/yarn
Then it hit me. In my .zshrc file, I had added the yarn global bin command (which spills out the directory of all the global packages installed by yarn) at the top like so:
# Top of my .zshrc file
export PATH="`yarn global bin`:$HOME/bin:/usr/local/bin:$PATH"
and as per the installation instruction of nvm, the $NVM_DIR (the variable which holds the nvm directory path) was added at the end of my .zshrc file.
So when I was starting up my shell, it was actually trying to load the yarn command (present inside the nvm directory) even before loading the $NVM_DIR path.
To solve this, I tweaked my .zshrc file and moved the yarn global bin command after the $NVM_DIR like this:
# Top of my .zshrc file
export PATH="$HOME/bin:/usr/local/bin:$PATH"
# ...
#
# Something in between
#
# ...
# Bottom of my .zshrc file
export NVM_DIR="${HOME}/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh" # This loads nvm
[ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion" # This loads nvm bash_completion
# Here is where I have added the path to yarn global
export PATH="`yarn global bin`:$$PATH"
I hope that this would be of help.

This solved it for me:
corepack enable
(if you get "Internal Error: EACCES: permission denied", run it with sudo)
This is also recommended by the Yarn documentation: https://yarnpkg.com/getting-started/install

Uninstall cmdtest:
sudo apt remove cmdtest
Then, run these commands:
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt update
sudo apt install yarn

If you want to avoid reboot, use
/usr/local/lib/node_modules/yarn/bin/yarn --version

The yarn documentation is missing a step, you need to restart your computer between this installation and running yarn --version.
This worked for me

I recently had a similar situation and here is how I solved it.
First I troubleshoot the current npm installation:
npm config -list
I had a ~/.npmrc file that had a different prefix:
PREFIX=/opt/homebrew
That made my npm installation look for globally installed packages under /opt/homebrew.
In my case, I'm using a different npm installation (not with homebrew anymore). A simple fix is to remove this custom PREFIX from the ~/.npmrc file and the problem was solved.
Now npm looks for globally installed packages under /usr/local/bin/.

I installed yarn with npm install -g yarn on git bash and I tested it with yarn -v that show the version of the installed yarn, but when I used yarn start it gives me this error
C:\Users\{username}\AppData\Roaming\npm/node_modules/node/bin/node: line 1: This: command not found
These are simple steps that I used to fix my problem on Windows 10:
Uninstall node.js
Restart your computer
Delete your C:\Program Files\nodejs and C:\Users\{username}\AppData\Roaming\npm
Install node.js again and check it with node -v
Start your vs code as an admin and write npm install
Write yarn start

REACT - not working npm while installing it

Did all the command on command line
from installing the npm globally npm install -g create-react-app along with following codes:
npx create-react-app <myprojectname>
and also cleared the npm cache but it always get stuck on the line in the image showing the following error. Along with the error:
┌──────────────────────────────────────────────────────────────────┐
│ npm update check failed │
│ Try running with sudo or get access │
│ to the local update config store via │
│ sudo chown -R $USER:$(id -gn $USER) C:\Users\Smart Sites\.config │
└──────────────────────────────────────────────────────────────────
along with 65 packages are looking for funding
[1]: https://i.stack.imgur.com/KJVVp.png

Here is what i found form the getting started page of create react app.
If you've previously installed create-react-app globally via
npm install -g create-react-app,
we recommend you uninstall the package using
npm uninstall -g create-react-app
to ensure that npx always uses the latest version.
npx create-react-app my-app
cd my-app
npm start
But always ensure that you have an existing folder before using npx.

Create React App with Storybook creating webpack issue

So I have a large React app created and set up with Create React App. Recently we started using Storybook to work on and create components. Its been great. However, we keep getting this weird webpack issue when we try to run or build the app. Here is the console log out:
> react-scripts start
There might be a problem with the project dependency tree.
It is likely not a bug in Create React App, but something you need to fix locally.
The react-scripts package provided by Create React App requires a dependency:
"webpack": "4.41.2"
Don't try to install it manually: your package manager does it automatically.
However, a different version of webpack was detected higher up in the tree:
/Users/alexanderkaran/Documents/ClimateClever/cc_school_web/node_modules/webpack (version: 4.41.5)
Manually installing incompatible versions is known to cause hard-to-debug issues.
If you would prefer to ignore this check, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
That will permanently disable this message but you might encounter other issues.
To fix the dependency tree, try following the steps below in the exact order:
1. Delete package-lock.json (not package.json!) and/or yarn.lock in your project folder.
2. Delete node_modules in your project folder.
3. Remove "webpack" from dependencies and/or devDependencies in the package.json file in your project folder.
4. Run npm install or yarn, depending on the package manager you use.
In most cases, this should be enough to fix the problem.
If this has not helped, there are a few other things you can try:
5. If you used npm, install yarn (http://yarnpkg.com/) and repeat the above steps with it instead.
This may help because npm has known issues with package hoisting which may get resolved in future versions.
6. Check if /Users/alexanderkaran/Documents/ClimateClever/cc_school_web/node_modules/webpack is outside your project directory.
For example, you might have accidentally installed something in your home folder.
7. Try running npm ls webpack in your project folder.
This will tell you which other package (apart from the expected react-scripts) installed webpack.
If nothing else helps, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
That would permanently disable this preflight check in case you want to proceed anyway.
P.S. We know this message is long but please read the steps above :-) We hope you find them helpful!
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! cc_school_web#0.1.0 start: `react-scripts start`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the cc_school_web#0.1.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR! /Users/alexanderkaran/.npm/_logs/2020-01-23T05_20_16_003Z-debug.log
alexanderkaran#AlexandersMBP2 cc_school_web %
I know what your thinking you must have installed webpack, well I didn't. When I run:
npm ls webpack
I get this log out:
cc_school_web#0.1.0 /Users/alexanderkaran/Documents/ClimateClever/cc_school_web
├─┬ #storybook/react#5.3.8
│ ├─┬ #storybook/core#5.3.8
│ │ ├─┬ corejs-upgrade-webpack-plugin#2.2.0
│ │ │ └── webpack#4.41.5 deduped
│ │ └── webpack#4.41.5 deduped
│ └── webpack#4.41.5
└─┬ react-scripts#3.3.0
└── webpack#4.41.2
alexanderkaran#AlexandersMBP2 cc_school_web %
So the issue seems to be to do with storybook. If I uninstall all npm modules and remove storybook, then re-add both everything works again but eventually, it breaks.
Does anyone have a fix for this? Or am I missing something?

Looks like this an issue with the version of Webpack Create React App uses being a few steps behind the version Storybook uses sometimes.
There is no fix, but there are some workarounds.
You can find more info on the issue here:
https://github.com/storybookjs/storybook/issues/6505
One workaround is to add SKIP_PREFLIGHT_CHECK=true to a .env file in your project.
This can cause issue though.
Another workaround is to keep using a version of storybook and create react app that works with each other and doesn't cause these issues. So do not just upgrade storybook straight if it contains a Webpack version bump.

Getting "bash: typeorm: command not found" after gloablly installing typeorm on linux

OS:
macOS Sierra v 10.12.6
I am trying to build an application in Typescript using the typeorm and this is my first time using either.
I've used both of the following to install typeorm:
npm i -g typeorm
&
sudo npm i -g typeorm
And am seeing the following in the terminal after installing:
+ typeorm#0.2.21
added 127 packages from 406 contributors in 7.081s
But when trying to use typeorm CLI commands:
typeorm init --name jwt-express-typeorm --database sqlite --express
I keep getting this error:
bash: typeorm: command not found
I've tried uninstalling the package globally using:
sudo uninstall typeorm -g --save
and reinstalling afterward but still getting the same error. Any help would would be super appreciated!

If you don't care to add the global node_modules folder (not just the project one) to your $PATH, you can use npx {command-name} instead. The global node_modules folder's location depends on your OS. See Where does npm install packages?. One benefit of using npx, however, is that it works with all packages, not just globally installed ones.

try appending npm run before typeorm

Running Express.js in Windows 7

I tried install express (using -g for global) in Windows 7 using
npm install -g express
I get the following and no errors:
npm http GET https://registry.npmjs.org/express
...
npm http GET https://registry.npmjs.org/mime/-/mime-1.2.11.tgz
npm http 200 https://registry.npmjs.org/mime/-/mime-1.2.11.tgz
npm http 304 https://registry.npmjs.org/debug/0.8.0
express#4.1.1 C:\Users\xxx\AppData\Roaming\npm\node_modules\express
├── methods#0.1.0
├── parseurl#1.0.1
..
├── type-is#1.1.0 (mime#1.2.11)
└── accepts#1.0.1 (negotiator#0.4.3, mime#1.2.11)
When I type express, I get:
'express' is not recognized as an internal or external command.
Any idea why this would happen?

I ran into the same problem on Windows 8.1
use this command
npm install -g express-generator
or
npm install -g express-generator#'version'
like
npm install -g express-generator#3

Express is not meant to be run on command prompt.
If you're trying to generate the base express project then you can use express-generator, you can install it using:
npm install -g express-generator
After success installtion, then to generate an express project:
Go the directory on your hard drive.
run the following command: express myProject
It will generate the base project for you.
using your command prompt go to the created folder by the previous command.
you can run now your project using one of the following commands:
npm start OR node myProject