How to guarantee non-existance of a file before creating? - node.js

fs.exists is now deprecated for a decent reason that I should try to open a file and catch error to be sure nothing is possible to delete the file in between checking and opening. But if I need to create a new file instead of opening an existing file, how do I guarantee that there is no file before I try to create it?

You can't. You can however, create a new file or open an existing one if it exists:
fs.open("/path", "a+", function(err, data){ // open for reading and appending
if(err) return handleError(err);
// work with file here, if file does not exist it will be created
});
Alternatively, open it with "ax+" which will error if it already exists, letting you handle the error.

module.exports = fs.existsSync || function existsSync(filePath){
try{
fs.statSync(filePath);
}catch(err){
if(err.code == 'ENOENT') return false;
}
return true;
};
https://gist.github.com/FGRibreau/3323836

https://stackoverflow.com/a/31545073/2435443
fs = require('fs') ;
var path = 'sth' ;
fs.stat(path, function(err, stat) {
if (err) {
if ('ENOENT' == err.code) {
//file did'nt exist so for example send 404 to client
} else {
//it is a server error so for example send 500 to client
}
} else {
//every thing was ok so for example you can read it and send it to client
}
} );

Related

Write a file into specific folder in node js?

Would like to write data into specific folder using writefile in node js.
I have seen couple of questions in stackoverflow regarding this but none of them worked for me .
For example :
fs.writeFile('./niktoResults/result.txt', 'This is my text', function (err) {
if (err) throw err;
console.log('Results Received');
});
This throws an error "NO SUCH FILE OR DIRECTORY"
Is there any alternative for writing data into specific folder node js ???
Ensure that the directory is available & accessible in the working directory.
In this case, a function like below needs to be called at the start of the application.
function initialize() {
const exists = fs.existsSync('./niktoResults');
if(exists === true) {
return;
}
fs.mkdirSync('./niktoResults')
}
Error caused by directory not existing, create a directory if it does not exist.
function create(text, directory, filename)
{
if (!fs.existsSync(directory)) {
fs.mkdirSync(directory);
console.log('Directory created');
create(text, directory);
} else {
fs.writeFile(`${directory}/${filename}`, `${text}`, function (error) {
if (error) {
throw error;
} else {
console.log('File created');
}
});
}
}
create('Text', 'directory', 'filename.txt');

fs.createWriteStream, no such file or directory, open Nodejs

I want to save files that I am getting from another server on my server but the problem is when I am calling createWriteStream it giving me the error :
no such file or directory, open
E:\pathtoproject\myproject\public\profile_14454.jpg
Here is my code which is in E:\pathtoproject\myproject\modules\dowload.js :
request.head(infos.profile_pic, function(err, res, body) {
const completeFileName = '../public/profile_14454.' + res.headers['content-type'].split('/')[1];
var imageStream = fs.createWriteStream(completeFileName);
imageStream.on('open', function(fd) {
console.log("File open");
request(infos.profile_pic).pipe(imageStream).on('close', function(body) {
consoleLog('Profile pic saved');
console.log('This is the content of body');
console.log(body);
connection.query('UPDATE user set photo=? where id=?', [completeFileName, lastID], function(err, result, fields) {
if (err) {
consoleLog('Error while update the profile pic');
}
});
})
});
});
When I removed the directory ../public/ and leave only the name of the file
profile_14454.' + res.headers['content-type'].split('/')[1] , it worked but the file was saved in the root directory of the project (E:\pathtoproject\myproject\).
What's wrong in what I am doing? How can I have the file saved under public directory?
I am using nodeJS 8.9.4
I tried with my small code .
var fs = require("fs");
var data = 'Simply Easy Learning';
// Create a writable stream
var writerStream = fs.createWriteStream('./airo/output.txt');
// Write the data to stream with encoding to be utf8
writerStream.write(data,'UTF8');
// Mark the end of file
writerStream.end();
// Handle stream events --> finish, and error
writerStream.on('finish', function() {
console.log("Write completed.");
});
writerStream.on('error', function(err){
console.log(err.stack);
});
console.log("Program Ended");
My code is in this path E:\syed ayesha\nodejs\nodejs now I want to store my file in airo folder which is in this path. So I used one dot for storing. Hope this helps.

fs.appendFile but fail if path does *not* exist

Looking through the fs docs, I am looking for a flag that I can use with fs.appendFile, where an error will be raised if the path does not exist.
I am seeing flags that pertain to raising errors if the path does already exist, but I am not seeing flags that will raise errors if the path does not exist -
https://nodejs.org/api/fs.html
First off, I assume you mean fs.appendFile(), since the fs.append() you refer to is not in the fs module.
There does not appear to be a flag that opens the file for appending that returns an error if the file does not exist. You could write one yourself. Here's a general idea for how to do so:
fs.appendToFileIfExist = function(file, data, encoding, callback) {
// check for optional encoding argument
if (typeof encoding === "function") {
callback = encoding;
encoding = 'utf8';
}
// r+ opens file for reading and writing. Error occurs if the file does
fs.open(file, 'r+', function(err, fd) {
if (err) return callback(err);
function done(err) {
fs.close(fd, function(close_err) {
fd = null;
if (!err && close_err) {
// if no error passed in and there was a close error, return that
return callback(close_err);
} else {
// otherwise return error passed in
callback(err);
}
});
}
// file is open here, call done(err) when we're done to clean up open file
// get length of file so we know how to append
fs.fstat(fd, function(err, stats) {
if (err) return done(err);
// write data to the end of the file
fs.write(fd, data, stats.size, encoding, function(err) {
done(err);
});
});
});
}
You could, of course, just test to see if the file exists before calling fs.appendFile(), but that is not recommended because of race conditions. Instead, it is recommended that you set the right flags on fs.open() and let that trigger an error if the file does not exist.

How to write file if parent folder doesn't exist?

I need to write file to the following path:
fs.writeFile('/folder1/folder2/file.txt', 'content', function () {…});
But '/folder1/folder2' path may not exists. So I get the following error:
message=ENOENT, open /folder1/folder2/file.txt
How can I write content to that path?
As of Node v10, this is built into the fs.mkdir function, which we can use in combination with path.dirname:
var fs = require('fs');
var getDirName = require('path').dirname;
function writeFile(path, contents, cb) {
fs.mkdir(getDirName(path), { recursive: true}, function (err) {
if (err) return cb(err);
fs.writeFile(path, contents, cb);
});
}
For older versions, you can use mkdirp:
var mkdirp = require('mkdirp');
var fs = require('fs');
var getDirName = require('path').dirname;
function writeFile(path, contents, cb) {
mkdirp(getDirName(path), function (err) {
if (err) return cb(err);
fs.writeFile(path, contents, cb);
});
}
If the whole path already exists, mkdirp is a noop. Otherwise it creates all missing directories for you.
This module does what you want: https://npmjs.org/package/writefile . Got it when googling for "writefile mkdirp". This module returns a promise instead of taking a callback, so be sure to read some introduction to promises first. It might actually complicate things for you.
The function I gave works in any case.
I find that the easiest way to do this is to use the outputFile() method from the fs-extra module.
Almost the same as writeFile (i.e. it overwrites), except that if the parent directory does not exist, it's created. options are what you'd pass to fs.writeFile().
Example:
var fs = require('fs-extra');
var file = '/tmp/this/path/does/not/exist/file.txt'
fs.outputFile(file, 'hello!', function (err) {
console.log(err); // => null
fs.readFile(file, 'utf8', function (err, data) {
console.log(data); // => hello!
});
});
It also has promise support out of the box these days!.
Edit
NodeJS version 10.12.0 has added a native support for both mkdir and mkdirSync to create the parent director recursively with recursive: true option as the following:
fs.mkdirSync(targetDir, { recursive: true });
And if you prefer fs Promises API, you can write
fs.promises.mkdir(targetDir, { recursive: true });
Original Answer
Create the parent directories recursively if they do not exist! (Zero dependencies)
const fs = require('fs');
const path = require('path');
function mkDirByPathSync(targetDir, { isRelativeToScript = false } = {}) {
const sep = path.sep;
const initDir = path.isAbsolute(targetDir) ? sep : '';
const baseDir = isRelativeToScript ? __dirname : '.';
return targetDir.split(sep).reduce((parentDir, childDir) => {
const curDir = path.resolve(baseDir, parentDir, childDir);
try {
fs.mkdirSync(curDir);
} catch (err) {
if (err.code === 'EEXIST') { // curDir already exists!
return curDir;
}
// To avoid `EISDIR` error on Mac and `EACCES`-->`ENOENT` and `EPERM` on Windows.
if (err.code === 'ENOENT') { // Throw the original parentDir error on curDir `ENOENT` failure.
throw new Error(`EACCES: permission denied, mkdir '${parentDir}'`);
}
const caughtErr = ['EACCES', 'EPERM', 'EISDIR'].indexOf(err.code) > -1;
if (!caughtErr || caughtErr && curDir === path.resolve(targetDir)) {
throw err; // Throw if it's just the last created dir.
}
}
return curDir;
}, initDir);
}
Usage
// Default, make directories relative to current working directory.
mkDirByPathSync('path/to/dir');
// Make directories relative to the current script.
mkDirByPathSync('path/to/dir', {isRelativeToScript: true});
// Make directories with an absolute path.
mkDirByPathSync('/path/to/dir');
Demo
Try It!
Explanations
[UPDATE] This solution handles platform-specific errors like EISDIR for Mac and EPERM and EACCES for Windows.
This solution handles both relative and absolute paths.
In the case of relative paths, target directories will be created (resolved) in the current working directory. To Resolve them relative to the current script dir, pass {isRelativeToScript: true}.
Using path.sep and path.resolve(), not just / concatenation, to avoid cross-platform issues.
Using fs.mkdirSync and handling the error with try/catch if thrown to handle race conditions: another process may add the file between the calls to fs.existsSync() and fs.mkdirSync() and causes an exception.
The other way to achieve that could be checking if a file exists then creating it, I.e, if (!fs.existsSync(curDir) fs.mkdirSync(curDir);. But this is an anti-pattern that leaves the code vulnerable to race conditions.
Requires Node v6 and newer to support destructuring. (If you have problems implementing this solution with old Node versions, just leave me a comment)
Perhaps most simply, you can just use the fs-path npm module.
Your code would then look like:
var fsPath = require('fs-path');
fsPath.writeFile('/folder1/folder2/file.txt', 'content', function(err){
if(err) {
throw err;
} else {
console.log('wrote a file like DaVinci drew machines');
}
});
With node-fs-extra you can do it easily.
Install it
npm install --save fs-extra
Then use the outputFile method instead of writeFileSync
const fs = require('fs-extra');
fs.outputFile('tmp/test.txt', 'Hey there!', err => {
if(err) {
console.log(err);
} else {
console.log('The file was saved!');
}
})
You can use
fs.stat('/folder1/folder2', function(err, stats){ ... });
stats is a fs.Stats type of object, you may check stats.isDirectory(). Depending on the examination of err and stats you can do something, fs.mkdir( ... ) or throw an error.
Reference
Update: Fixed the commas in the code.
Here's my custom function to recursively create directories (with no external dependencies):
var fs = require('fs');
var path = require('path');
var myMkdirSync = function(dir){
if (fs.existsSync(dir)){
return
}
try{
fs.mkdirSync(dir)
}catch(err){
if(err.code == 'ENOENT'){
myMkdirSync(path.dirname(dir)) //create parent dir
myMkdirSync(dir) //create dir
}
}
}
myMkdirSync(path.dirname(filePath));
var file = fs.createWriteStream(filePath);
Here is my function which works in Node 10.12.0. Hope this will help.
const fs = require('fs');
function(dir,filename,content){
fs.promises.mkdir(dir, { recursive: true }).catch(error => { console.error('caught exception : ', error.message); });
fs.writeFile(dir+filename, content, function (err) {
if (err) throw err;
console.info('file saved!');
});
}
Here's part of Myrne Stol's answer broken out as a separate answer:
This module does what you want: https://npmjs.org/package/writefile .
Got it when googling for "writefile mkdirp". This module returns a
promise instead of taking a callback, so be sure to read some
introduction to promises first. It might actually complicate things
for you.
let name = "./new_folder/" + file_name + ".png";
await driver.takeScreenshot().then(
function(image, err) {
require('mkdirp')(require('path').dirname(name), (err) => {
require('fs').writeFile(name, image, 'base64', function(err) {
console.log(err);
});
});
}
);
In Windows you can use this code:
try {
fs.writeFileSync( './/..//..//filename.txt' , 'the text to write in the file', 'utf-8' );
}
catch(e){
console.log(" catch XXXXXXXXX ");
}
This code in windows create file in 2 folder above the current folder.
but I Can't create file in C:\ Directly

Different results from asynchronous and synchronous reading

I have a fairly simple script that attempts to read and then parse a JSON file. The JSON is very simple and I am pretty sure it is valid.
{
"foo": "bar"
}
Now, I have been trying to read it with fs.readFile. When read no errors occur and the returned data is a string. The only problem is that the string is empty.
I repeated my code but used fs.readFileSync, this returned the file perfectly using the same path. Both had a utf-8 encoding specified.
It is very simple code, as you can see.
fs.readFile('./some/path/file.json', 'utf8', function(err, data) {
if(!err) {
console.log(data); // Empty string...
}
});
console.log(fs.readFileSync('./some/path/file.json', 'utf8')); // Displays JSON file
Could it be permissions or ownership? I have tried a permission set of 755 and 777 to no avail.
I am running node v0.4.10. Any suggestions to point me in the right direction will be much appreciated. Thanks.
Edit: Here is a block of my actual code. Hopefully this will give you a better idea.
// Make sure the file is okay
fs.stat(file, function(err, stats) {
if(!err && stats.isFile()) {
// It is okay. Now load the file
fs.readFile(file, 'utf-8', function(readErr, data) {
if(!readErr && data) {
// File loaded!
// Now attempt to parse the config
try {
parsedConfig = JSON.parse(data);
self.mergeConfig(parsedConfig);
// The config was loaded and merged
// We can now call the callback
// Pass the error as null
callback.call(self, null);
// Share the news about the new config
self.emit('configLoaded', file, parsedConfig, data);
}
catch(e) {
callback.call(self, new Error(file + ': The config file is not valid JSON.'));
}
}
else {
callback.call(self, new Error(file + ': The config file could not be read.'));
}
});
}
else {
callback.call(self, new Error(file + ': The config file does not exist.'));
}
});
This is pretty weird.
The code looks.
var fs = require('fs');
fs.readFile('./jsonfile', 'utf8', function(err, data) {
if(err) {
console.error(err);
} else {
console.log(data);
parsedConfig = JSON.parse(data);
console.log(parsedConfig);
console.log(parsedConfig.foo);
}
});
Json file:
{
"foo": "bar"
}
output :
$ node test_node3.js
{
"foo": "bar"
}
{ foo: 'bar' }
bar
This is on node 0.4.10 , but i'm pretty sure it should work on all node version.
So why your data is empty ? You should check err in this case (like mine) and post the output if any. If you have no error, you may fill a bug on github

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