This example finds the size of a specified directory, giving results for both the total size of the directory as well as the total size of the files contained in the directory. The reduce plug-in is used to accumulate the total sizes of each constituent of the directory.

The state machine has two states, ReadDir and CalcSize. The ReadDir state reads the target directory and passes its contents in an array to the CalcSize state. This state then uses the reduce plug-in to iterate over the array, calling the fs.lstat function for each element. The returned stats object is then used to update the memo object to contain the total sizes for both the desired results.

function dirSize (fire, dirPath) {
  this.startState = 'ReadDir';
  this.states = {
    ReadDir: {
      async: 'fs.readdir',
      actions: {
        '.done': 'CalcSize',
        '.err': '@error'
      }
    },

    CalcSize: {
      reduce: {
        fn: 'fs.lstat',
        iterator: function (memo, stats) {          
          if (stats.isFile()) {
            memo.file += stats.size;
          }
          memo.all += stats.size;
          return memo;
        },
        memo: { 
          file: 0, 
          all: 0 
        }
      },
      actions: {
        '.done': '@exit',
        '.err': '@error'
      }
    }
  }; 
};

dirSize.defaults = {
  imports: { fs: require('fs') },
  args: [ '.' ],
  callback: function (err, size) {
    if (!err) {
      console.log('Directory size: files only=%d, all items=%d', 
          size.file, size.all);
    }
  }
};

module.exports = dirSize;

 $ ./bin/ignite examples/plugins/reduce/dir_size.js
 Running examples/plugins/reduce/dir_size.js
 run: examples/plugins/reduce/dir_size.js Exited with no error.
 Directory size: files only=5799, all items=46759
 $ _

 $ ./bin/ignite examples/plugins/reduce/dir_size.js badpath
 Running examples/plugins/reduce/dir_size.js
 run: examples/plugins/reduce/dir_size.js Exited with error:
 ENOENT, No such file or directory
 $ _