folders(5) folders(5)
NAME
folders - 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.
tl;dr
o Local install (default): puts stuff in ./node_modules of the
current package root.
o Global install (with -g): puts stuff in /usr/local or wherever node
is installed.
o Install it locally if you're going to require() it.
o Install it globally if you're going to run it on the command line.
o If you need both, then install it in both places, or use npm link.
prefix Configuration
The prefix config </using-npm/config#prefix> defaults to the location
where node is installed. On most systems, this is /usr/local. On
Windows, it's %AppData%\npm. On Unix systems, it's one level up, since
node is typically installed at {prefix}/bin/node rather than
{prefix}/node.exe.
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 dropped 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/lib/path/to/sub/module") to load other modules.
Global installs on Unix systems go to {prefix}/lib/node_modules. Global
installs on Windows go to {prefix}/node_modules (that is, no lib
folder.)
Scoped packages are installed the same way, except they are grouped
together in a sub-folder of the relevant node_modules folder with the
name of that scope prefix by the @ symbol, e.g. npm install
@myorg/package would place the package in
{prefix}/node_modules/@myorg/package. See npm help scope for more
details.
If you wish to require() a package, then install it locally.
Executables
When in global mode, executables are linked into {prefix}/bin on Unix,
or directly into {prefix} on Windows. Ensure that path is in your
terminal's PATH environment to run them.
When in local mode, executables are linked into ./node_modules/.bin so
that they can be made available to scripts run through npm. (For
example, so that a test runner will be in the path when you run npm
test.)
Man Pages
When in global mode, man pages are linked into {prefix}/share/man.
When in local mode, man pages are not installed.
Man pages are not installed on Windows systems.
Cache
See npm help cache. Cache files are stored in ~/.npm on Posix, or
%LocalAppData%/npm-cache on Windows.
This is controlled by the cache config </using-npm/config#cache> param.
Temp Files
Temporary files are stored by default in the folder specified by the
tmp config </using-npm/config#tmp>, which defaults to the TMPDIR, TMP,
or TEMP environment variables, or /tmp on Unix and c:\windows\temp on
Windows.
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 installing locally, npm first tries to find an appropriate prefix
folder. This is so that npm install foo@1.2.3 will install to the
sensible root of your package, even if you happen to have cded into
some other folder.
Starting at the $PWD, npm will walk up the folder tree checking for a
folder that contains either a package.json file, or a node_modules
folder. If such a thing is found, then that is treated as the effective
"current directory" for the purpose of running npm commands. (This
behavior is inspired by and similar to git's .git-folder seeking logic
when running git commands in a working dir.)
If no package root is found, then the current folder is used.
When you run npm install foo@1.2.3, then the package is loaded into the
cache, and then unpacked into ./node_modules/foo. Then, any of foo's
dependencies are similarly unpacked into
./node_modules/foo/node_modules/....
Any bin files are symlinked to ./node_modules/.bin/, so that they may
be found by npm scripts when necessary.
Global Installation
If the global config </using-npm/config#global> is set to true, then
npm will install packages "globally".
For global installation, packages are installed roughly the same way,
but using the folders described above.
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 baz 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 (hoisting).
Since version 3, npm hoists dependencies by default.
Example
Consider this dependency graph:
foo
+-- blerg@1.2.5
+-- bar@1.2.3
| +-- blerg@1.x (latest=1.3.7)
| +-- 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 (with all
dependencies hoisted to the highest level possible):
foo
+-- node_modules
+-- blerg (1.2.5) <---[A]
+-- bar (1.2.3) <---[B]
| +-- node_modules
| +-- baz (2.0.2) <---[C]
+-- asdf (2.3.4)
+-- baz (1.2.3) <---[D]
+-- quux (3.2.0) <---[E]
Since foo depends directly on bar@1.2.3 and baz@1.2.3, those are
installed in foo's node_modules folder.
Even though the latest copy of blerg is 1.3.7, foo has a specific
dependency on version 1.2.5. So, that gets installed at [A]. Since the
parent installation of blerg satisfies bar's dependency on blerg@1.x,
it does not install another copy under [B].
Bar [B] also has dependencies on baz and asdf. Because it depends on
baz@2.x, it cannot re-use the baz@1.2.3 installed in the parent
node_modules folder [D], and must install its own copy [C]. In order to
minimize duplication, npm hoists dependencies to the top level by
default, so asdf is installed under [A].
Underneath bar, the baz -> quux -> bar dependency creates a cycle.
However, because bar is already in quux's ancestry [B], it does not
unpack another copy of bar into that folder. Likewise, quux's [E]
folder tree is empty, because its dependency on bar is satisfied by the
parent folder copy installed at [B].
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 not in the bundleDependencies 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. See package.json </configuring-npm/package-
json> for more information.
See also
o package.json </configuring-npm/package-json>
o npm help install
o npm help pack
o npm help cache
o npm help config
o npm help npmrc
o npm help config
o npm help publish
June 2023 folders(5)
npm 9.7.1 - Generated Mon Jun 12 11:07:43 CDT 2023