Ubuntu Manpage: npm-scripts - How npm handles the "scripts" field

NAME

       npm-scripts - How npm handles the "scripts" field

DESCRIPTION

       npm supports the "scripts" property of the package.json file, for the following scripts:

       · prepublish:  Run  BEFORE  the  package  is packed and published, as well as on local npm
         install without any arguments. (See below)

       · prepare: Run both BEFORE the package is packed and published, and on local  npm  install
         without   any   arguments  (See  below).  This  is  run  AFTER  prepublish,  but  BEFORE
         prepublishOnly.

       · prepublishOnly: Run BEFORE the package is prepared and packed, ONLY on npm publish. (See
         below.)

       · prepack:  run  BEFORE a tarball is packed (on npm pack, npm publish, and when installing
         git dependencies)

       · postpack: Run AFTER the tarball has been generated and moved to its final destination.

       · publish, postpublish: Run AFTER the package is published.

       · preinstall: Run BEFORE the package is installed

       · install, postinstall: Run AFTER the package is installed.

       · preuninstall, uninstall: Run BEFORE the package is uninstalled.

       · postuninstall: Run AFTER the package is uninstalled.

       · preversion: Run BEFORE bumping the package version.

       · version: Run AFTER bumping the package version, but BEFORE commit.

       · postversion: Run AFTER bumping the package version, and AFTER commit.

       · pretest, test, posttest: Run by the npm test command.

       · prestop, stop, poststop: Run by the npm stop command.

       · prestart, start, poststart: Run by the npm start command.

       · prerestart, restart, postrestart: Run by the npm restart command. Note: npm restart will
         run the stop and start scripts if no restart script is provided.

       · preshrinkwrap, shrinkwrap, postshrinkwrap: Run by the npm shrinkwrap command.

       Additionally, arbitrary scripts can be executed by running npm run-script <stage>. Pre and
       post commands with matching names will  be  run  for  those  as  well  (e.g.  premyscript,
       myscript,  postmyscript).  Scripts  from dependencies can be run with npm explore <pkg> --
       npm run <stage>.

PREPUBLISH AND PREPARE

   DEPRECATION NOTE
       Since npm@1.1.71, the npm CLI has run the prepublish script for both npm publish  and  npm
       install, because it's a convenient way to prepare a package for use (some common use cases
       are described in the section below).  It has also turned out  to  be,  in  practice,  very
       confusing  https://github.com/npm/npm/issues/10074.  As of npm@4.0.0, a new event has been
       introduced, prepare, that preserves this existing behavior. A  new  event,  prepublishOnly
       has  been  added as a transitional strategy to allow users to avoid the confusing behavior
       of existing npm versions and only run on npm publish (for instance, running the tests  one
       last time to ensure they're in good shape).

       See  https://github.com/npm/npm/issues/10074  for  a  much  lengthier  justification, with
       further reading, for this change.

   USE CASES
       If you need to perform operations on your package before it is used, in a way that is  not
       dependent  on  the operating system or architecture of the target system, use a prepublish
       script.  This includes tasks such as:

       · Compiling CoffeeScript source code into JavaScript.

       · Creating minified versions of JavaScript source code.

       · Fetching remote resources that your package will use.

       The advantage of doing these things at prepublish time is that they can be done once, in a
       single place, thus reducing complexity and variability.  Additionally, this means that:

       · You  can  depend  on coffee-script as a devDependency, and thus your users don't need to
         have it installed.

       · You don't need to include minifiers in your package, reducing the size for your users.

       · You don't need to rely on your users having curl or wget or other system  tools  on  the
         target machines.

DEFAULT VALUES

       npm will default some script values based on package contents.

       · "start":  "node  server.js":  If  there is a server.js file in the root of your package,
         then npm will default the start command to node server.js.

       · "install": "node-gyp rebuild": If there is a  binding.gyp  file  in  the  root  of  your
         package and you haven't defined your own install or preinstall scripts, npm will default
         the install command to compile using node-gyp.

USER

       If npm was invoked with root privileges, then it will change the uid to the  user  account
       or  uid  specified by the user config, which defaults to nobody.  Set the unsafe-perm flag
       to run scripts with root privileges.

ENVIRONMENT

       Package scripts run in an environment where many pieces of information are made  available
       regarding the setup of npm and the current state of the process.

   path
       If  you  depend  on  modules  that define executable scripts, like test suites, then those
       executables will be added to the PATH for executing the scripts.  So, if your package.json
       has this:

         { "name" : "foo"
         , "dependencies" : { "bar" : "0.1.x" }
         , "scripts": { "start" : "bar ./test" } }

       then  you  could  run  npm  start  to  execute  the bar script, which is exported into the
       node_modules/.bin directory on npm install.

   package.json vars
       The package.json fields are tacked onto the npm_package_ prefix. So, for instance, if  you
       had {"name":"foo", "version":"1.2.5"} in your package.json file, then your package scripts
       would  have  the  npm_package_name  environment   variable   set   to   "foo",   and   the
       npm_package_version set to "1.2.5"

   configuration
       Configuration  parameters  are  put  in  the  environment with the npm_config_ prefix. For
       instance, you  can  view  the  effective  root  config  by  checking  the  npm_config_root
       environment variable.

   Special: package.json config object
       The  package.json  "config"  keys  are overwritten in the environment if there is a config
       param of <name>[@<version>]:<key>.  For example, if the package.json has this:

         { "name" : "foo"
         , "config" : { "port" : "8080" }
         , "scripts" : { "start" : "node server.js" } }

       and the server.js is this:

         http.createServer(...).listen(process.env.npm_package_config_port)

       then the user could change the behavior by doing:

         npm config set foo:port 80

   current lifecycle event
       Lastly, the npm_lifecycle_event environment variable is set  to  whichever  stage  of  the
       cycle  is  being  executed. So, you could have a single script used for different parts of
       the process which switches based on what's currently happening.

       Objects    are    flattened    following    this     format,     so     if     you     had
       {"scripts":{"install":"foo.js"}} in your package.json, then you'd see this in the script:

         process.env.npm_package_scripts_install === "foo.js"

EXAMPLES

       For example, if your package.json contains this:

         { "scripts" :
           { "install" : "scripts/install.js"
           , "postinstall" : "scripts/install.js"
           , "uninstall" : "scripts/uninstall.js"
           }
         }

       then  scripts/install.js  will  be  called  for the install and post-install stages of the
       lifecycle, and scripts/uninstall.js will be called when the package is uninstalled.  Since
       scripts/install.js  is  running for two different phases, it would be wise in this case to
       look at the npm_lifecycle_event environment variable.

       If you want to run a make command, you can do so.  This works just fine:

         { "scripts" :
           { "preinstall" : "./configure"
           , "install" : "make && make install"
           , "test" : "make test"
           }
         }

EXITING

       Scripts are run by passing the line as a script argument to sh.

       If the script exits with a code other than 0, then this will abort the process.

       Note that these script files don't have to be nodejs or  even  javascript  programs.  They
       just have to be some kind of executable file.

HOOK SCRIPTS

       If  you want to run a specific script at a specific lifecycle event for ALL packages, then
       you can use a hook script.

       Place an executable file at node_modules/.hooks/{eventname}, and it'll  get  run  for  all
       packages  when they are going through that point in the package lifecycle for any packages
       installed in that root.

       Hook scripts are run exactly the same way as package.json scripts.  That is, they are in a
       separate child process, with the env described above.

BEST PRACTICES

· Don't exit with a non-zero error code unless you really mean it. Except for uninstall
scripts, this will cause the npm action to fail, and potentially be rolled back. If the
failure is minor or only will prevent some optional features, then it's better to just
print a warning and exit successfully.

· Try not to use scripts to do what npm can do for you. Read through npm help 5
package.json to see all the things that you can specify and enable by simply describing
your package appropriately. In general, this will lead to a more robust and consistent
state.

· Inspect the env to determine where to put things. For instance, if the
npm_config_binroot environment variable is set to /home/user/bin, then don't try to
install executables into /usr/local/bin. The user probably set it up that way for a
reason.

· Don't prefix your script commands with "sudo". If root permissions are required for
some reason, then it'll fail with that error, and the user will sudo the npm command in
question.

· Don't use install. Use a .gyp file for compilation, and prepublish for anything else.
You should almost never have to explicitly set a preinstall or install script. If you
are doing this, please consider if there is another option. The only valid use of
install or preinstall scripts is for compilation which must be done on the target
architecture.