How does `CI=true` affect the `npm install` command?

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I'm having trouble finding good documentation on how the CI=true effects the npm install command.

How is CI=true npm install different from npm install. Does the CI=true even effect the install?

I tried it locally and it does NOT cause it to behave like npm ci. I tried running it without the package-lock.json or npm-shrinkwrap.json file present. It created the lock file.

Also, is there a difference between

CI=true npm install

and

CI=true 
npm install

and

export CI=true 
npm install
npm node.js
1 Answers

Setting the CI environment variable to true effects how npm gathers usage data.

How it effects npm is explained in the Does npm send any information about me back to the registry section of the docs (For convenience, I've provided a verbatim copy of that section below). Consider particularly the description about the Npm-In-CI header.

In summary, setting CI=true causes npm to set the Npm-In-CI header to true, thus as a result the data gathered (by npm) assumes the package(s) are being installed via a "build farm", (i.e. for Continuous Integration purposes), instead of a "human".

The following is what is stated in the docs at the aforementioned link:

Does npm send any information about me back to the registry?

Yes.

When making requests of the registry npm adds two headers with information about your environment:

  • Npm-Scope – If your project is scoped, this header will contain its scope. In the future npm hopes to build registry features that use this information to allow you to customize your experience for your organization.
  • Npm-In-CI – Set to “true” if npm believes this install is running in a continuous integration environment, “false” otherwise. This is detected by looking for the following environment variables: CI, TDDIUM, JENKINS_URL, bamboo.buildKey. If you’d like to learn more you may find the original PR interesting. This is used to gather better metrics on how npm is used by humans, versus build farms.

With regards to the specific part of your question, i.e.

Does the CI=true even effect the install?

Generally "No", there is no notable difference to the resultant installation by npm with or without CI=true.

However, a possible scenario whereby the installation of a package by npm could/may be effected, is if a package author defined a postinstall script in package.json that performed different conditional logic if/when the CI environment variable is set to true.

Regarding the last part of your question, i.e.

Also, is there a difference between ...

The accepted answer to this question addresses that.

In summary;

  • Your first two commands are similar - they both set the environment variable for the current shell only.
  • However your last example that utilizes export sets the environment variable for the current shell and all processes started from the current shell.
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