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.