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NPM-INSTALL(1) NPM-INSTALL(1)

NAME

npm-install - Install a package

SYNOPSIS

npm install (with no args, in package dir)
npm install [<@scope>/]<name>
npm install [<@scope>/]<name>@<tag>
npm install [<@scope>/]<name>@<version>
npm install [<@scope>/]<name>@<version range>
npm install <git-host>:<git-user>/<repo-name>
npm install <git repo url>
npm install <tarball file>
npm install <tarball url>
npm install <folder>
alias: npm i common options: [-P|--save-prod|-D|--save-dev|-O|--save-optional] [-E|--save-exact] [-B|--save-bundle] [--no-save] [--dry-run]

DESCRIPTION

This command installs a package, and any packages that it depends on. If the package has a package-lock or shrinkwrap file, the installation of dependencies will be driven by that, with an npm-shrinkwrap.json taking precedence if both files exist. See npm help 5 package-lock.json and npm help shrinkwrap.
A package is:
a) a folder containing a program described by a npm help 5 package.json file
b) a gzipped tarball containing (a)
c) a url that resolves to (b)
d) a <name>@<version> that is published on the registry (see npm help 7 npm-registry) with (c)
e) a <name>@<tag> (see npm help npm-dist-tag) that points to (d)
f) a <name> that has a "latest" tag satisfying (e)
g) a <git remote url> that resolves to (a)
Even if you never publish your package, you can still get a lot of benefits of using npm if you just want to write a node program (a), and perhaps if you also want to be able to easily install it elsewhere after packing it up into a tarball (b).
npm install (in package directory, no arguments):
Install the dependencies in the local node_modules folder.
In global mode (ie, with -g or --global appended to the command),
it installs the current package context (ie, the current working
directory) as a global package.
By default, npm install will install all modules listed as dependencies
in npm help 5 package.json.
With the --production flag (or when the NODE_ENV environment variable
is set to production), npm will not install modules listed in
devDependencies. NOTE: The --production flag has no particular meaning when adding a
dependency to a project.
npm install <folder>:
Install the package in the directory as a symlink in the current project.
Its dependencies will be installed before it's linked. If <folder> sits
inside the root of your project, its dependencies may be hoisted to the
toplevel node_modules as they would for other types of dependencies.
npm install <tarball file>:
Install a package that is sitting on the filesystem. Note: if you just want
to link a dev directory into your npm root, you can do this more easily by
using npm link. The filename must use .tar, .tar.gz, or .tgz as
the extension.
Example:
    npm install ./package.tgz
npm install <tarball url>:
Fetch the tarball url, and then install it. In order to distinguish between
this and other options, the argument must start with "http://" or "https://"
Example:
npm install [<@scope>/]<name>:
Do a <name>@<tag> install, where <tag> is the "tag" config. (See
npm help 7 npm-config. The config's default value is latest.)
In most cases, this will install the version of the modules tagged as
latest on the npm registry.
Example:
    npm install sax

npm install saves any specified packages into dependencies by default.
Additionally, you can control where and how they get saved with some
additional flags:
-P, --save-prod: Package will appear in your dependencies. This is the
               default unless `-D` or `-O` are present.
-D, --save-dev: Package will appear in your devDependencies.
-O, --save-optional: Package will appear in your optionalDependencies.
--no-save: Prevents saving to dependencies. When using any of the above options to save dependencies to your package.json, there are two additional, optional flags:
-E, --save-exact: Saved dependencies will be configured with an exact version rather than using npm's default semver range operator.
-B, --save-bundle: Saved dependencies will also be added to your bundleDependencies list. Further, if you have an npm-shrinkwrap.json or package-lock.json then it will be updated as well. <scope> is optional. The package will be downloaded from the registry associated with the specified scope. If no registry is associated with the given scope the default registry is assumed. See npm help 7 npm-scope. Note: if you do not include the @-symbol on your scope name, npm will interpret this as a GitHub repository instead, see below. Scopes names must also be followed by a slash. Examples:
npm install sax
npm install githubname/reponame
npm install @myorg/privatepackage
npm install node-tap --save-dev
npm install dtrace-provider --save-optional
npm install readable-stream --save-exact
npm install ansi-regex --save-bundle
**Note**: If there is a file or folder named `<name>` in the current
working directory, then it will try to install that, and only try to
fetch the package by name if it is not valid.
npm install [<@scope>/]<name>@<tag>:
Install the version of the package that is referenced by the specified tag.
If the tag does not exist in the registry data for that package, then this
will fail.
Example:
    npm install sax@latest
    npm install @myorg/mypackage@latest
npm install [<@scope>/]<name>@<version>:
Install the specified version of the package. This will fail if the
version has not been published to the registry.
Example:
    npm install sax@0.1.1
    npm install @myorg/privatepackage@1.5.0
npm install [<@scope>/]<name>@<version range>:
Install a version of the package matching the specified version range. This
will follow the same rules for resolving dependencies described in npm help 5 package.json.
Note that most version ranges must be put in quotes so that your shell will
treat it as a single argument.
Example:
    npm install sax@">=0.1.0 <0.2.0"
    npm install @myorg/privatepackage@">=0.1.0 <0.2.0"
npm install <git remote url>:
Installs the package from the hosted git provider, cloning it with git.
For a full git remote url, only that URL will be attempted.
    <protocol>://[<user>[:<password>]@]<hostname>[:<port>][:][/]<path>[#<commit-ish> | #semver:<semver>]

<protocol> is one of git, git+ssh, git+http, git+https, or
git+file.
If #<commit-ish> is provided, it will be used to clone exactly that
commit. If the commit-ish has the format #semver:<semver>, <semver> can
be any valid semver range or exact version, and npm will look for any tags
or refs matching that range in the remote repository, much as it would for a
registry dependency. If neither #<commit-ish> or #semver:<semver> is
specified, then master is used.
If the repository makes use of submodules, those submodules will be cloned
as well.
If the package being installed contains a prepare script, its
dependencies and devDependencies will be installed, and the prepare
script will be run, before the package is packaged and installed.
The following git environment variables are recognized by npm and will be
added to the environment when running git:
GIT_ASKPASS
GIT_EXEC_PATH
GIT_PROXY_COMMAND
GIT_SSH
GIT_SSH_COMMAND
GIT_SSL_CAINFO
GIT_SSL_NO_VERIFY See the git man page for details. Examples:
npm install git+ssh://git@github.com:npm/npm.git#v1.0.27
npm install git+ssh://git@github.com:npm/npm#semver:^5.0
npm install git+https://isaacs@github.com/npm/npm.git
npm install git://github.com/npm/npm.git#v1.0.27
GIT_SSH_COMMAND='ssh -i ~/.ssh/custom_ident' npm install git+ssh://git@github.com:npm/npm.git
npm install <githubname>/<githubrepo>[#<commit-ish>]:
npm install github:<githubname>/<githubrepo>[#<commit-ish>]:
Install the package at https://github.com/githubname/githubrepo by
attempting to clone it using git.
If #<commit-ish> is provided, it will be used to clone exactly that
commit. If the commit-ish has the format #semver:<semver>, <semver> can
be any valid semver range or exact version, and npm will look for any tags
or refs matching that range in the remote repository, much as it would for a
registry dependency. If neither #<commit-ish> or #semver:<semver> is
specified, then master is used.
As with regular git dependencies, dependencies and devDependencies will
be installed if the package has a prepare script, before the package is
done installing.
Examples:
    npm install mygithubuser/myproject
    npm install github:mygithubuser/myproject
npm install gist:[<githubname>/]<gistID>[#<commit-ish>|#semver:<semver>]:
Install the package at https://gist.github.com/gistID by attempting to
clone it using git. The GitHub username associated with the gist is
optional and will not be saved in package.json.
As with regular git dependencies, dependencies and devDependencies will
be installed if the package has a prepare script, before the package is
done installing.
Example:
    npm install gist:101a11beef
npm install bitbucket:<bitbucketname>/<bitbucketrepo>[#<commit-ish>]:
Install the package at https://bitbucket.org/bitbucketname/bitbucketrepo
by attempting to clone it using git.
If #<commit-ish> is provided, it will be used to clone exactly that
commit. If the commit-ish has the format #semver:<semver>, <semver> can
be any valid semver range or exact version, and npm will look for any tags
or refs matching that range in the remote repository, much as it would for a
registry dependency. If neither #<commit-ish> or #semver:<semver> is
specified, then master is used.
As with regular git dependencies, dependencies and devDependencies will
be installed if the package has a prepare script, before the package is
done installing.
Example:
    npm install bitbucket:mybitbucketuser/myproject
npm install gitlab:<gitlabname>/<gitlabrepo>[#<commit-ish>]:
Install the package at https://gitlab.com/gitlabname/gitlabrepo
by attempting to clone it using git.
If #<commit-ish> is provided, it will be used to clone exactly that
commit. If the commit-ish has the format #semver:<semver>, <semver> can
be any valid semver range or exact version, and npm will look for any tags
or refs matching that range in the remote repository, much as it would for a
registry dependency. If neither #<commit-ish> or #semver:<semver> is
specified, then master is used.
As with regular git dependencies, dependencies and devDependencies will
be installed if the package has a prepare script, before the package is
done installing.
Example:
    npm install gitlab:mygitlabuser/myproject
    npm install gitlab:myusr/myproj#semver:^5.0
You may combine multiple arguments, and even multiple types of arguments. For example:
npm install sax@">=0.1.0 <0.2.0" bench supervisor
The --tag argument will apply to all of the specified install targets. If a tag with the given name exists, the tagged version is preferred over newer versions.
The --dry-run argument will report in the usual way what the install would have done without actually installing anything.
The --package-lock-only argument will only update the package-lock.json, instead of checking node_modules and downloading dependencies.
The -f or --force argument will force npm to fetch remote resources even if a local copy exists on disk.
npm install sax --force
The -g or --global argument will cause npm to install the package globally rather than locally. See npm help 5 npm-folders.
The --global-style argument will cause npm to install the package into your local node_modules folder with the same layout it uses with the global node_modules folder. Only your direct dependencies will show in node_modules and everything they depend on will be flattened in their node_modules folders. This obviously will eliminate some deduping.
The --ignore-scripts argument will cause npm to not execute any scripts defined in the package.json. See npm help 7 npm-scripts.
The --legacy-bundling argument will cause npm to install the package such that versions of npm prior to 1.4, such as the one included with node 0.8, can install the package. This eliminates all automatic deduping.
The --link argument will cause npm to link global installs into the local space in some cases.
The --no-bin-links argument will prevent npm from creating symlinks for any binaries the package might contain.
The --no-optional argument will prevent optional dependencies from being installed.
The --no-shrinkwrap argument, which will ignore an available package lock or shrinkwrap file and use the package.json instead.
The --no-package-lock argument will prevent npm from creating a package-lock.json file. When running with package-lock's disabled npm will not automatically prune your node modules when installing.
The --nodedir=/path/to/node/source argument will allow npm to find the node source code so that npm can compile native modules.
The --only={prod[uction]|dev[elopment]} argument will cause either only devDependencies or only non-devDependencies to be installed regardless of the NODE_ENV.
See npm help 7 npm-config. Many of the configuration params have some effect on installation, since that's most of what npm does.

ALGORITHM

To install a package, npm uses the following algorithm:
load the existing node_modules tree from disk
clone the tree
fetch the package.json and assorted metadata and add it to the clone
walk the clone and add any missing dependencies
  dependencies will be added as close to the top as is possible
  without breaking any other modules
compare the original tree with the cloned tree and make a list of
actions to take to convert one to the other
execute all of the actions, deepest first
  kinds of actions are install, update, remove and move
For this package{dep} structure: A{B,C}, B{C}, C{D}, this algorithm produces:
A
+-- B
+-- C
+-- D
That is, the dependency from B to C is satisfied by the fact that A already caused C to be installed at a higher level. D is still installed at the top level because nothing conflicts with it.
For A{B,C}, B{C,D@1}, C{D@2}, this algorithm produces:
A
+-- B
+-- C
   `-- D@2
+-- D@1
Because B's D@1 will be installed in the top level, C now has to install D@2 privately for itself. This algorithm is deterministic, but different trees may be produced if two dependencies are requested for installation in a different order.
See npm help 5 folders for a more detailed description of the specific folder structures that npm creates.

Limitations of npm's Install Algorithm

npm will refuse to install any package with an identical name to the current package. This can be overridden with the --force flag, but in most cases can simply be addressed by changing the local package name.
There are some very rare and pathological edge-cases where a cycle can cause npm to try to install a never-ending tree of packages. Here is the simplest case:
A -> B -> A' -> B' -> A -> B -> A' -> B' -> A -> ...
where A is some version of a package, and A' is a different version of the same package. Because B depends on a different version of A than the one that is already in the tree, it must install a separate copy. The same is true of A', which must install B'. Because B' depends on the original version of A, which has been overridden, the cycle falls into infinite regress.
To avoid this situation, npm flat-out refuses to install any name@version that is already present anywhere in the tree of package folder ancestors. A more correct, but more complex, solution would be to symlink the existing version into the new location. If this ever affects a real use-case, it will be investigated.

SEE ALSO

npm help 5 folders
npm help update
npm help link
npm help rebuild
npm help 7 scripts
npm help build
npm help config
npm help 7 config
npm help 5 npmrc
npm help 7 registry
npm help dist-tag
npm help uninstall
npm help shrinkwrap
npm help 5 package.json
October 2018