Write input of a npm command to a variable but only a specific part

Question

On my root directory of my project, I have a package.json. While doing the CI build, I am trying to capture the version properties from the file. Since I am running on a node container, the following command is possible.

node -p -e require('./package.json').version

I included the above in scripts property of package.json

  "scripts": {
     "version": "node -p -e require('./package.json').version"
   },

I am capturing it in a variable using

export VERSION=$(npm run version)

which seems to capture a lot more than the result of the npm command. Build environment is a Nodejs10 container built on rhel7.

jq is not available and something without it may be better

Any suggestions?

Answer 1

1. Change your npm script to:

   "scripts": {
     "version": "node -p \"require('./package.json').version\""
   }
   

   The -e option is not necessary, also the JavaScript to be evaluated must be passed as a string. Note it's been encased in JSON escaped double quotes, i.e. \".

2. Also capture and export it using the following code instead:

   export VERSION=$(npm run version -s)
   

   Note the additional -s option (which is the shorthand for --silent) - this ensures you capture only the version (e.g. 1.0.0) and not the additional npm log info.

Answer 2

packege.json can reference itself using the following pattern

$npm_package_PROP[_SUB_PROP][_SUB_SUB_PROP]

  "version": "1.0.0",
  "scripts": {
    ...
    "version": "echo $npm_package_version"
  },

npm run version # output: 1.0.0