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
<pkg> <stage>.
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.
-
SEE ALSO¶
- •
- npm help run-script
- •
- npm help package.json
- •
- npm help developers
- •
- npm help install
-
-