npm-folders(1) -- Folder Structures Used by npm =============================================== ## DESCRIPTION npm puts various things on your computer. That's its job. This document will tell you what it puts where. ### prefix Configuration The `prefix` config defaults to node's `process.installPrefix`. On most systems, this is `/usr/local`. When the `global` flag is set, npm installs things into this prefix. When it is not set, it uses the root of the current package, or the current working directory if not in a package already. ### Node Modules Packages are droped into the `node_modules` folder under the `prefix`. When installing locally, this means that you can `require("packagename")` to load its main module, or `require("packagename/path/to/sub/module")` to load other modules. If you wish to install node modules globally which can be loaded via `require()` from anywhere, then add the `prefix/node_modules` folder to your NODE_PATH environment variable. ### Executables When in global mode, executables are linked into `prefix/bin`. When in local mode, executables are linked into `prefix/node_modules/.bin`. ### Man Pages When in global mode, man pages are linked into `prefix/share/man`. When in local node, man pages are not installed. ### Cache See `npm help cache`. Cache files are stored in `~/.npm` on Posix, or `~/npm-cache` on Windows. This is controlled by the `cache` configuration param. ### Temp Files Temporary files are stored by default in the folder specified by the `tmp` config, which defaults to either the TMPDIR environment variable, or `/tmp`. Temp files are given a unique folder under this root for each run of the program, and are deleted upon successful exit. ## More Information When you run `npm install foo@1.2.3` it downloads and builds the package, and then, if there is a package.json file in the current working directory, it copies it to `$PWD/node_modules/foo`, so that your current package will get it when you do `require("foo")`. When this is done, it also installs all of foo's dependencies to `./node_modules/foo/node_modules/`, so that it will get its dependencies appropriately when it calls `require()`. If foo depends on bar, and bar depends on baz, then there will also be a `./node_modules/foo/node_modules/bar/node_modules/baz`, and so on. If there is not a package.json in the current working directory, then npm walks up the working dir parent paths looking for a package.json, indicating the root of a package, or a node_modules folder, indicating an npm package deployment location, and then take the party to that location. This behavior may be suppressed by setting the `seek-root` config value to false. If no package root is found, then a global installation is performed. The global installation may be supressed by setting the `global` configuration to false, in which case, the install will fail. ### Global Installation If the `global` configuration is set to true, or if it is not explicitly set false and no suitable node_modules folder was found, then npm will install packages "globally". This means that the module contents are symlinked (or, on windows, copied) from `root///package` to `root/node_modules/`. ### Cycles, Conflicts, and Folder Parsimony Cycles are handled using the property of node's module system that it walks up the directories looking for node_modules folders. So, at every stage, if a package is already installed in an ancestor node_modules folder, then it is not installed at the current location. Consider the case above, where `foo -> bar -> baz`. Imagine if, in addition to that, baz depended on bar, so you'd have: `foo -> bar -> baz -> bar -> baz ...`. However, since the folder structure is: foo/node_modules/bar/node_modules/baz, there's no need to put another copy of bar into .../baz/node_modules, since when it calls require("bar"), it will get the copy that is installed in foo/node_modules/bar. This shortcut is only used if the exact same version would be installed in multiple nested node_modules folders. It is still possible to have `a/node_modules/b/node_modules/a` if the two "a" packages are different versions. However, without repeating the exact same package multiple times, an infinite regress will always be prevented. Another optimization can be made by installing dependencies at the highest level possible, below the localized "target" folder. For example, consider this dependency graph: foo +-- bar@1.2.3 | +-- baz@2.x | | `-- quux@3.x | | `-- bar@1.2.3 (cycle) | `-- asdf@* `-- baz@1.2.3 `-- quux@3.x `-- bar In this case, we might expect a folder structure like this: foo +-- node_modules +-- bar (1.2.3) | +-- node_modules | | `-- baz (2.0.2) | | `-- node_modules | | `-- quux (3.2.0) | `-- asdf (2.3.4) `-- baz (1.2.3) `-- node_modules `-- quux (3.2.0) `-- node_modules `-- bar (1.2.3) `-- node_modules `-- asdf (2.3.4) Since foo depends directly on bar@1.2.3 and baz@1.2.3, those are installed in foo's node_modules folder. Bar has dependencies on baz and asdf, so those are installed in bar's node_modules folder. Baz has a dependency on quux, so that is installed in its node_modules folder. Underneath bar, the `baz->quux->bar` dependency creates a cycle. However, because `bar` is already in `quux`'s ancestry, it does not unpack another copy of bar into that folder. Similarly, underneath `foo->baz`, the same cycle is gradually prevented because `bar`'s `quux` dependency is satisfied by its parent folder. For a graphical breakdown of what is installed where, use `npm ls`. ### Publishing Upon publishing, npm will look in the node_modules folder. If any of the items there are on the "dependencies" or "devDependencies" list, and are not in the `bundledDependencies` array, then they will not be included in the package tarball. This allows a package maintainer to install all of their dependencies (and dev dependencies) locally, but only re-publish those items that cannot be found elsewhere.