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npm-install(1) -- 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 <tarball file>
npm install <tarball url>
npm install <folder>

alias: npm i
common options: [-S|--save|-D|--save-dev|-O|--save-optional] [-E|--save-exact] [-B|--save-bundle] [--dry-run]

DESCRIPTION

This command installs a package, and any packages that it depends on. If the package has a shrinkwrap file, the installation of dependencies will be driven by that. See npm-shrinkwrap(1).

A package is:

a) a folder containing a program described by a package.json(5) 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-registry(7)) with (c)
e) a <name>@<tag> (see npm-dist-tag(1)) 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 package.json(5).

With the --production flag (or when the NODE_ENV environment variable is set to production), npm will not install modules listed in devDependencies.
npm install <folder>:

Install a package that is sitting in a folder on the filesystem.
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.

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 https://github.com/indexzero/forever/tarball/v0.5.6
```
npm install [<@scope>/]<name> [-S|--save|-D|--save-dev|-O|--save-optional]:

Do a <name>@<tag> install, where <tag> is the "tag" config. (See npm-config(7). The config's default value is latest.)

In most cases, this will install the latest version of the module published on npm.

Example:
```
    npm install sax
```
npm install takes 3 exclusive, optional flags which save or update the package version in your main package.json:
- -S, --save: Package will appear in your dependencies.
- -D, --save-dev: Package will appear in your devDependencies.
- -O, --save-optional: Package will appear in your optionalDependencies.
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 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-scope(7).

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 --save
    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 --save-exact
    npm install ansi-regex --save --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 package.json(5).

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. First it tries via the https (git with github) and if that fails, via ssh.
```
    <protocol>://[<user>[:<password>]@]<hostname>[:<port>][:][/]<path>[#<commit-ish>]
```
<protocol> is one of git, git+ssh, git+http, git+https, or git+file. If no <commit-ish> is specified, then master is used.

If the repository makes use of submodules, those submodules will be cloned as well.

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+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 you don't specify a commit-ish then master will be used.

Examples:
```
    npm install mygithubuser/myproject
    npm install github:mygithubuser/myproject
```
npm install gist:[<githubname>/]<gistID>[#<commit-ish>]:

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 if -S or --save is used.

If you don't specify a commit-ish then master will be used.

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 you don't specify a commit-ish then master will be used.

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 you don't specify a commit-ish then master will be used.

Example:
```
    npm install gitlab:mygitlabuser/myproject
```

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 -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-folders(5).

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-scripts(7).

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 shrinkwrap file and use the package.json instead.

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-config(7). 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.

See npm-folders(5) for a more detailed description of the specific folder structures that npm creates.

Limitations of npm's Install Algorithm

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.

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