ParsedFileOutput package

• FileOutput
• SplitFileOutput
• ParsedFileOutput
• Parser

FileOutput function

Returns the output (stdout) of an executable command as an iterable stream or as a string.

Usage/Examples

import the package

const { FileOutput } = require('fileOutput');

instantiate a process with no arguments

const stdout = FileOutput({ file: '/path/to/file' });

or instantiate a process with arguments

const stdout = FileOutput({ file: '/path/to/file', args: ['arg1', 'arg2'] });

get the entire output as string

console.log(await stdout().asString());

or read the output as an iterable stream

for await (const chunk of stdout().asStream()) {
  console.log(chunk);
}

it is also possible to pass additional arguments to the process in the call

console.log(await stdout(['arg3']).asString());

SplitFileOutput function

Returns the output (stdout) of an executable command split by a delimiter as an iterable stream.

Usage/Examples

import the package

const { SplitFileOutput } = require('splitFileOutput');

instantiate a process similar to FileOutput, but with a string or RegExp delimiter (defaults to /\r?\n/ if none specified)

const stdout = SplitFileOutput({ file: '/path/to/file', delimiter: '\n' });

or

const stdout = SplitFileOutput({ file: '/path/to/file', delimiter: /\n/ });

read output split to items as an iterable stream

for await (const split of stdout().asSplits()) {
  console.log(split);
}

ParsedFileOutput function

Returns the output (stdout) of an executable command split by a delimiter and applied a parser function to each as an iterable stream.

Usage/Examples

import the package

const { ParsedFileOutput } = require('parsedFileOutput');

instantiate a process similar to SplitFileOutput, but with a parser function. Basically it is a function, that converts text input (the split) to anything you want, i.e. an object.

const parser = (text) => ({ data: text, length: text.length });

For more complex examples of the parser function, see section below.

const stdout = ParsedFileOutput({
  file: '/path/to/file',
  delimiter: '\n',
  parser,
});

read parsed output split to items as an iterable stream

for await (const item of stdout().asItems()) {
  console.log(item);
}

or read parsed output split to items as an array

const items = stdout().asArray();
console.log(items);

Parser function

Returns a function, that converts a text to object with predefined fields.

Usage/Examples

import the package

const { Parser } = require('parsedFileOutput');

Instantiate the function with fields definition.

const parser = Parser({ fields });

You can specify a separator (either string or RegExp, defaults to , if none specified) and/or a quote character (defaults to ").

const parser = Parser({ fields, separator: ';', quote: '`' });

You can specify one or more of three functions:

• split
• assign
• cast

The split function

This function has two arguments, the text input and a default separate function (i.e. converts delimiter separated values to array). It should return an array.

The simplest use case is only to manipulate the text input:

const split = (text) => ['begin', text, 'end'];

If the function is omitted, behind the scenes the parser executes as if it would be:

const split = (text, separate) => separate(text);

You can also alter the return array before returning it from the function:

const split = (text, separate) => {
  const result = separate(text);
  result.map((i) => i.toUpperString());
  return result;
};

The assign function

This function has two arguments, the array input (result of the split function) and a default assign function (i.e. assign values from array to fields, one after another). It should return an object.

The simplest use case is only to manipulate the array input:

const assign = (array) => ({
  timeStamp: new Date(),
  author: array[0],
  title: array[1],
});

If the function is omitted, behind the scenes the parser executes as if it would be:

const assign = (array, assign) => assign(array);

You can also alter the return array before returning it from the function:

const assign = (array, assign) => {
  const result = assign(array);
  result.hash = calculateSHA(JSON.stringify(result));
  return result;
};

The cast function

This function has two arguments, a value and the field. It should return a value of any type.

The simplest use case is only to manipulate the value:

const cast = (value) => `###${value}###`;

If the function is omitted, behind the scenes the parser executes as if it would be:

const cast = (value, field) => value;

You can also alter the value before returning it from the function:

const cast = (value, field) => {
  let result = value;
  if (field.type === 'number') value = parseInt(value);
  return result;
};