A command-line tool can be used to build a client. When the build property is a string, truffle assumes that we want to run a command to build the client, so it runs the string as a command. The command is given ample environment variables with which to integrate with truffle.

You can make truffle run a command-line tool to build the client using similar configuration code:

module.exports = { 
  // This will run the `webpack` command on each build. 
  // 
  // The following environment variables will be set when running the command: 
  // WORKING_DIRECTORY: root location of the project 
  // BUILD_DESTINATION_DIRECTORY: expected destination of built assets 
  // BUILD_CONTRACTS_DIRECTORY: root location of your build contract files (.sol.js) 
  // 
  build: "webpack" 
}