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

NAME

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

DESCRIPTION

       npm supports the "scripts" member 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.

       preupdate
              Run BEFORE the package is updated with the update command.

       update, postupdate
              Run AFTER the package is updated with the update command.

       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 run by doing npm run-script <stage> <pkg>.

NOTE: INSTALL SCRIPTS ARE AN ANTIPATTERN

tl;dr 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. In early versions of node, this was often done using the
node-waf scripts, or a standalone Makefile, and early versions of npm required that it be
explicitly set in package.json. This was not portable, and harder to do properly.

In the current version of node, the standard way to do this is using a .gyp file. If you
have a file with a .gyp extension in the root of your package, then npm will run the
appropriate node-gyp commands automatically at install time. This is the only officially
supported method for compiling binary addons, and does not require that you add anything
to your package.json file.

If you have to do other things before your package is used, in a way that is not dependent
on the operating system or architecture of the target system, then use a prepublish script
instead. This includes tasks such as:

• Compile CoffeeScript source code into JavaScript.

• Create minified versions of JavaScript source code.

• Fetching remote resources that your package will use.

The advantage of doing these things at prepublish time instead of preinstall or install
time is that they can be done once, in a single place, and thus greatly reduce 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 the 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.

       "preinstall": "node-waf clean || true; node-waf configure build":

              If there is a wscript file in the root  of  your  package,  npm  will  default  the
              preinstall command to compile using node-waf.

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.

       •   npm  help   Try  not  to  use  scripts  to  do  what  npm can do for you. Read through
           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  environ  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.