Ubuntu Manpage: npm-folders - Folder Structures Used by npm

NAME

       npm-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
• Local install (default): puts stuff in ./node_modules of the current package root.

• Global install (with -g): puts stuff in /usr/local or wherever node is installed.

• Install it locally if you´re going to require() it.

• Install it globally if you´re going to run it on the command line.

• If you need both, then install it in both places, or use npm link.

prefix Configuration
The prefix config defaults to the location where node is installed. On most systems, this
is /usr/local, and most of the time is the same as node´s process.installPrefix.

On windows, this is the exact location of the node.exe binary. 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.)

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.

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
npm help See npm-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 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 configuration 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 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.

   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:

           foo
           +-- node_modules
               +-- blerg (1.2.5) <---[A]
               +-- bar (1.2.3) <---[B]
               |   `-- node_modules
               |       +-- baz (2.0.2) <---[C]
               |       |   `-- node_modules
               |       |       `-- quux (3.2.0)
               |       `-- asdf (2.3.4)
               `-- baz (1.2.3) <---[D]
                   `-- node_modules
                       `-- 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,  so  those  are  installed  in  bar´s
       node_modules  folder.  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].

       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.

       Underneath  foo -> baz [D], 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  bundledDependencies  array,  then  they  will not be included in the package
       tarball.

       This allows a package maintainer to install all of their dependencies (npm help   and  dev
       dependencies) locally, but only re-publish those items that cannot be found elsewhere. See
       package.json for more information.

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