module

fs

File-system module.

Example

// import module
var fs = require('qminer').fs;
// open file in write mode
var fout = fs.openWrite('file.txt');
// write sync and close
fout.writeLine('example text');
fout.close();
// open file in read mode
var fin = fs.openRead('file.txt');
// read a line
var str = fin.readLine();

Child classes

FIn(fileName)

FOut(fileName[, append])

Methods

copy(source, dest)
del(fileName)
exists(fileName)
fileInfo(fileName)
listFile(dirName[, fileExtension][, recursive])

mkdir(dirName)
move(source, dest)
openAppend(fileName)
openRead(fileName)
openWrite(fileName)

readCsvLines(buffer, opts)
readLines(buffer, onLine(line), onEnd(err))
rename(source, dest)
rmdir(dirName)

Abstract type

FileInfo

Classes

Methods

static

copy(source, dest)

Copies a file.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('text.txt');
// close the stream
fout.close();
// copy the file
// var destination = fs.copy('text.txt', 'copy.txt');

Parameters

Name	Type	Optional	Description
source	string		Source file name.
dest	string		Destination file name.

static

del(fileName) → boolean

Deletes a file.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('delete.txt');
// close the stream
fout.close();
// delete the file
var destination = fs.del('delete.txt');

Parameter

Name	Type	Optional	Description
fileName	string		File name.

Returns: booleanB True if delete succeeded.

static

exists(fileName) → boolean

Checks if the file exists.

Example

// import fs module
var fs = require('qminer').fs;
// check if a file exists
fs.exists('text.txt');

Parameter

Name	Type	Optional	Description
fileName	string		File name.

Returns: booleanB True if file exists.

static

fileInfo(fileName) → module:fs~FileInfo

Returns the file info.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('text.txt');
// close the stream
fout.close();
// get the file info
var info = fs.fileInfo('text.txt');

Parameter

Name	Type	Optional	Description
fileName	string		File name.

Returns: module:fs~FileInfoB File info object.

static

listFile(dirName[, fileExtension][, recursive]) → Array of string

Returns a list fo files in the folder.

Example

// import fs module
var fs = require('qminer').fs;
// get the names of all files
var fileNames = fs.listFile('./');

Parameters

Name Type Optional Description

dirName

string

Folder name.

fileExtension

string

Yes

Results are filtered by file extension.

recursive

boolean

Yes

Recursively searches for file names if true.

Defaults to false.

Returns: Array of stringB Array of file names.

static

mkdir(dirName) → boolean

Creates a folder.

Example

// import fs module
var fs = require('qminer').fs;
// create a folder
var makeFolder = fs.mkdir('folder');

Parameter

Name	Type	Optional	Description
dirName	string		Folder name.

Returns: booleanB True if succeeded.

static

move(source, dest)

Moves a file.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('text.txt');
// close the stream
fout.close();
// move the file
// var destination = fs.move('text.txt', 'move.txt');

Parameters

Name	Type	Optional	Description
source	string		Source file name.
dest	string		Destination file name.

static

openAppend(fileName) → module:fs.FOut

Open file in append mode and return file output stream.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('append_text.txt');
// close the stream
fout.close();
// open file in append mode
var foutAppend = fs.openAppend('append_text.txt');
// close the stream
foutAppend.close();

Parameter

Name	Type	Optional	Description
fileName	string		File name.

Returns: module:fs.FOutB Output stream.

static

openRead(fileName) → module:fs.FIn

Open file in read mode and return file input stream.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('read_text.txt');
// write to file
fout.write('This is awesome!');
// close the stream
fout.close();
// open file to read
var fin = fs.openRead('read_text.txt');

Parameter

Name	Type	Optional	Description
fileName	string		File name.

Returns: module:fs.FInB Input stream.

static

openWrite(fileName) → module:fs.FOut

Open file in write mode and return file output stream.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('write_text.txt');
// close the stream
fout.close();

Parameter

Name	Type	Optional	Description
fileName	string		File name.

Returns: module:fs.FOutB Output stream.

static

readCsvLines(buffer, opts)

Reads a buffer, containing a CSV file, line by line and calls a callback for each line. As specified in CSV format standard defined in RFC 4180 double-quotes (") can be used as escape characters. If a double-quote appears in a field, the field nust be enclosed in double-quotes and the double-quote appearing inside a field must be escaped by preceding it with another double quote. The callback function accepts an array with the values of the current line.

Example

// import fs module                                                                                                                                   
let fs = require('qminer').fs;                                                                                                                        
// create a file and write some lines                                                                                                                 
let fout = fs.openWrite('test.csv');                                                                                                                  
fout.write('name,movie\nGeorge Clooney,"O Brother, Where Art Thou?"\n"Sylvester ""Sly"" Stallone",Expendables');                                      
fout.close();                                                                                                                                         
// open the file in read mode                                                                                                                         
let fin = fs.openRead('test.csv');                                                                                                                    
// prepare callbacks for csv parsing                                                                                                                  
// count the lines and for each line output the parsed cells                                                                                          
let nLines = 0;                                                                                                                                       
function onLine(lineVals) {                                                                                                                           
    nLines += 1;                                                                                                                                      
    console.log(lineVals);                                                                                                                            
    return true;                                                                                                                                      
}                                                                                                                                                     
// at the end output the number of lines                                                                                                              
function onEnd(err) {                                                                                                                                 
    if (err) { console.log("Error:", err); }                                                                                                          
    console.log("Number of lines", nLines);                                                                                                           
}                                                                                                                                                     
// parse the csv files                                                                                                                                
fs.readCsvLines(fin, {                                                                                                                                
    "onLine": onLine,                                                                                                                                 
    "onEnd": onEnd                                                                                                                                    
});

Parameters

Name Type Optional Description

buffer

Buffer

The Node.js buffer.

opts

Object

Options parameter.

Values in opts have the following properties:

Name	Type	Description
onLine	function()	A callback that gets called on each line (for example: `function (lineArr) {}`).
onEnd	function()	A callback that gets returned after all the lines have been read.
delimiter	String	The delimiter used when parsing.
lineLimit	Number	The maximum number of lines read.
skipLines	Number	The number of lines that should be skipped before first calling the callback.

static

readLines(buffer, onLine(line), onEnd(err))

Reads a buffer line by line and calls a callback for each line.

Example

// import fs module
var fs = require('qminer').fs;
// create a file and write some lines
var fout = fs.openWrite('poem.txt');
fout.write('I dig,\nYou dig,\nHe digs,\nShe digs,\nWe dig,\nThey dig.\n It\'s not a beautiful poem, but it\'s deep.');
fout.close();
// open the file in read mode
var fin = fs.openRead('poem.txt');
// read the file line by line and call functions
var numberOfLines = 0;
function onLine(line) {
    console.log(line);
    numberOfLines += 1;
    return true;
}
function onEnd(err) {
    if (err) { console.log("Error:", err); }
    console.log("Number of lines", numberOfLines);
}
fs.readLines(fin, onLine, onEnd);

Parameters

Name	Type	Description
buffer	(String, module:fs.FIn, or Buffer)	Name of the file, input stream of a Node.js buffer.
onLine(line)	function()	A callback that gets called on each line (for example: `function (line) {}`). Function must return `true` to continue reading, else reading is stoped and `onEnd` is called.
onEnd(err)	function()	A callback that gets returned after all the lines have been read or function `onLine` returned `false`. If error was due to exception, the exception is provided in `err`.

static

rename(source, dest)

Renames a file.

Example

// import fs module
var fs = require('qminer').fs;
// open file to write
var fout = fs.openWrite('text.txt');
// close the stream
fout.close();
// rename the file
if (fs.exists('rename.txt')) {
   fs.del('rename.txt');
}
var destination = fs.rename('text.txt', 'rename.txt');

Parameters

Name	Type	Optional	Description
source	string		Source file name.
dest	string		Destination file name.

static

rmdir(dirName) → boolean

Removes a folder.

Example

// import fs module
var fs = require('qminer').fs;
// create a folder
var makeFolder = fs.mkdir('folder');
// delete folder
if (makeFolder) {
   fs.rmdir('folder');
}

Parameter

Name	Type	Optional	Description
dirName	string		Folder name.

Returns: booleanB True if succeeded.

Abstract type

inner

FileInfo Object

Information about the file.

Properties

Name	Type	Description
createTime	string	Create time.
lastAccessTime	string	Last access time.
lastWriteTime	string	Last write time.
size	number	File size in bytes.