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 script, for the following scripts:

       prepublish
              Run BEFORE the package is published. (Also run on local npm install without any arguments.)

       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, version
              Run BEFORE bump the package version.

       postversion
              Run AFTER bump the package version.

       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.

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

COMMON USES

       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, 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
       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  the  scripts/install.js  will be called for the install, post-install, stages of the lifecycle, and
       the scripts/uninstall.js would be called when the package is  uninstalled.  Since  scripts/install.js  is
       running  for  three  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.