I'm trying to write a small app that installs some files and modules in a new folder, but I keep getting this error:
{ Error: ENOENT: no such file or directory, uv_chdir
at process.chdir (/home/aboardwithabag/LaunchProject/node_modules/graceful-fs/polyfills.js:20:9)
at cd (/home/aboardwithabag/LaunchProject/index.js:26:13)
Below is my code. Can someone help me out?
// node LaunchProject projectName
// Installs a server, node modules, and index page.
// not working due to issues with chdir.
const cp = require('child_process');
const fse = require('fs-extra');
// const path = require('path');
const project = process.argv[2];
let server ="";
let home = "";
function make (cb){
fse.mkdirs(project, function(err){
if (err){
console.error(err);
}
});
cb;
}
function cd(cb){
try{
process.chdir('/'+project);
cb;
} catch (err) {
console.error(err);
return;
}}
function install(cb){
cp.exec('npm install express', function(err){
if (err){
console.error(err);
} else {
console.log('Express Installed.');
cp.exec('npm install ejs', function(err){
if (err){
console.error(err);
} else{
console.log('Ejs Installed.');
fse.outputFile('index.js', server);
fse.outputFile('public/index.html', home);
}});
}
});
cb;
}
make(cd(install(console.log(project + ' created.'))));
unless the folder name you assign to the project variable (in this case it seems to be "uv_chdir") is located at the root folder of your HDD, below line will give the error:
process.chdir('/'+project);
make sure you give correct path to the program arguments. (in this case argv[2])
Or you may remove the leading '/' and make the path relative.
It seems there are some issues with this code.
cb callbacks provided as function arguments need to be called not after the async calls, but inside the callbacks of these calls. For example:
function make (cb){
fse.mkdirs(project, function(err){
if (err){
console.error(err);
}
cb();
});
}
The last call chain make(cd(install(console.log(project + ' created.')))); would work only with sync calls in reversed order and only if they returned needed callbacks.
That is why your new dir is not ready when you try to use it: your async functions do not actually wait for each other.
You do not call your callbacks as cb(), just mention them as cb. You should call them.
With minimal changess, your code can be refactored in this way:
'use strict';
const cp = require('child_process');
const fse = require('fs-extra');
const project = process.argv[2];
let server = '';
let home = '';
make(cd, install, () => { console.log(project + ' created.'); });
function make(cb1, cb2, cb3) {
fse.mkdirs(project, (err) => {
if (err) {
console.error(err);
}
cb1(cb2, cb3);
});
}
function cd(cb1, cb2) {
try {
process.chdir('/' + project);
cb1(cb2);
} catch (err) {
console.error(err);
}
}
function install(cb1) {
cp.exec('npm install express', (err) => {
if (err) {
console.error(err);
} else {
console.log('Express Installed.');
cp.exec('npm install ejs', (err) => {
if (err) {
console.error(err);
} else {
console.log('Ejs Installed.');
fse.outputFile('index.js', server);
fse.outputFile('public/index.html', home);
cb1();
}
});
}
});
}
But it is rather brittle and unnecessarily complicated in this form. Maybe it would be simpler to inline your functions each in other.
when I use PM2,i got this error "no such file or directory, uv_chdir"
the resolvent is :
first,I use 'pm2 delete' to delete old process
second,I use 'pm2 start',then ok
ps : just change your code or use 'pm2 reload' or 'pm2 restart' would not be ok.
more detail , you can see "https://blog.csdn.net/u013934914/article/details/51145134"
I am trying to process some directories under a specific path. one of the directories contains some folders. actually, i do not have
access to all these folders, because some of them are my own and the others belong to other users.
my question is, is there any way in javascript to check the access rights of a specific folder? because what I want to do is, to check first if I have
access to open and see the contents of that folder or not. if I have access to it, then the logic will continue. if i do not have the right to open that
folder, then i will do something else.
please let me know how to check the my access rights of a folder or a file
Note:
I am using Ubuntu
try this
var fs = require('fs');
fs.access(__dirname, fs.constants.R_OK, function(err) {
if(err){
console.error("can't read");
process.exit(1);
}
console.log("can read");
process.exit(0);
});
same way you can check for write and executable access
you can find the documentation here
You can use fs for your task
var file= 'test.text'
// Check if the file exists in the current directory.
fs.access(file, fs.constants.F_OK, (err) => {
console.log(`${file} ${err ? 'does not exist' : 'exists'}`);
});
// Check if the file is readable.
fs.access(file, fs.constants.R_OK, (err) => {
console.log(`${file} ${err ? 'is not readable' : 'is readable'}`);
});
// Check if the file is writable.
fs.access(file, fs.constants.W_OK, (err) => {
console.log(`${file} ${err ? 'is not writable' : 'is writable'}`);
});
// Check if the file exists in the current directory, and if it is writable.
fs.access(file, fs.constants.F_OK | fs.constants.W_OK, (err) => {
if (err) {
console.error(
`${file} ${err.code === 'ENOENT' ? 'does not exist' : 'is read-only'}`);
} else {
console.log(`${file} exists, and it is writable`);
}
});
More details
What i'm trying to do is read/write to multiple files at once, Once a file is created, only the data inside the file would be changed.
code:
var files = fs.readdirSync(__dirname+"/")
function readWrite(files) {
fs.readFile(files[i], 'utf-8', function(err, data){
if (err){
console.log(err)
}
fs.writeFile(files[i], 'test string', 'utf-8', function (err) {
if (err){
console.log("completed")
}
})
})
}
for(i in files){
readWrite(files[i])
}
The error is pretty obvious "path must be a string", But how do I go about writing to multiple files in the same directory at once?
I'm pretty new to node, so sorry if this seems like a bonehead question, any help would be appreciated.
You're passing filename to readWrite function so you should not use [i]:
function readWrite(file) {
fs.readFile(file, 'utf-8', function(err, data) {
if (err) {
console.log(err)
}
fs.writeFile(file, 'test string', 'utf-8', function (err) {
if (err) {
console.log("completed")
}
})
})
}
for (i in files) {
readWrite(files[i])
}
Try replacing files[i] by files inside your function. You should be using the name of your variable, files (and probably rename it to filepath)
After that, do you really want to read and write from the same file at the same time (this is what your code is doing) ?
I am trying to append a string to a log file. However writeFile will erase the content each time before writing the string.
fs.writeFile('log.txt', 'Hello Node', function (err) {
if (err) throw err;
console.log('It\'s saved!');
}); // => message.txt erased, contains only 'Hello Node'
Any idea how to do this the easy way?
For occasional appends, you can use appendFile, which creates a new file handle each time it's called:
Asynchronously:
const fs = require('fs');
fs.appendFile('message.txt', 'data to append', function (err) {
if (err) throw err;
console.log('Saved!');
});
Synchronously:
const fs = require('fs');
fs.appendFileSync('message.txt', 'data to append');
But if you append repeatedly to the same file, it's much better to reuse the file handle.
When you want to write in a log file, i.e. appending data to the end of a file, never use appendFile. appendFile opens a file handle for each piece of data you add to your file, after a while you get a beautiful EMFILE error.
I can add that appendFile is not easier to use than a WriteStream.
Example with appendFile:
console.log(new Date().toISOString());
[...Array(10000)].forEach( function (item,index) {
fs.appendFile("append.txt", index+ "\n", function (err) {
if (err) console.log(err);
});
});
console.log(new Date().toISOString());
Up to 8000 on my computer, you can append data to the file, then you obtain this:
{ Error: EMFILE: too many open files, open 'C:\mypath\append.txt'
at Error (native)
errno: -4066,
code: 'EMFILE',
syscall: 'open',
path: 'C:\\mypath\\append.txt' }
Moreover, appendFile will write when it is enabled, so your logs will not be written by timestamp. You can test with example, set 1000 in place of 100000, order will be random, depends on access to file.
If you want to append to a file, you must use a writable stream like this:
var stream = fs.createWriteStream("append.txt", {flags:'a'});
console.log(new Date().toISOString());
[...Array(10000)].forEach( function (item,index) {
stream.write(index + "\n");
});
console.log(new Date().toISOString());
stream.end();
You end it when you want. You are not even required to use stream.end(), default option is AutoClose:true, so your file will end when your process ends and you avoid opening too many files.
Your code using createWriteStream creates a file descriptor for every write. log.end is better because it asks node to close immediately after the write.
var fs = require('fs');
var logStream = fs.createWriteStream('log.txt', {flags: 'a'});
// use {flags: 'a'} to append and {flags: 'w'} to erase and write a new file
logStream.write('Initial line...');
logStream.end('this is the end line');
Besides appendFile, you can also pass a flag in writeFile to append data to an existing file.
fs.writeFile('log.txt', 'Hello Node', {'flag':'a'}, function(err) {
if (err) {
return console.error(err);
}
});
By passing flag 'a', data will be appended at the end of the file.
Use a+ flag to append and create a file (if doesn't exist):
fs.writeFile('log.txt', 'Hello Node', { flag: "a+" }, (err) => {
if (err) throw err;
console.log('The file is created if not existing!!');
});
Docs: https://nodejs.org/api/fs.html#fs_file_system_flags
You need to open it, then write to it.
var fs = require('fs'), str = 'string to append to file';
fs.open('filepath', 'a', 666, function( e, id ) {
fs.write( id, 'string to append to file', null, 'utf8', function(){
fs.close(id, function(){
console.log('file closed');
});
});
});
Here's a few links that will help explain the parameters
open
write
close
EDIT: This answer is no longer valid, look into the new fs.appendFile method for appending.
My approach is rather special. I basically use the WriteStream solution but without actually 'closing' the fd by using stream.end(). Instead I use cork/uncork. This got the benefit of low RAM usage (if that matters to anyone) and I believe it's more safe to use for logging/recording (my original use case).
Following is a pretty simple example. Notice I just added a pseudo for loop for showcase -- in production code I am waiting for websocket messages.
var stream = fs.createWriteStream("log.txt", {flags:'a'});
for(true) {
stream.cork();
stream.write("some content to log");
process.nextTick(() => stream.uncork());
}
uncork will flush the data to the file in the next tick.
In my scenario there are peaks of up to ~200 writes per second in various sizes. During night time however only a handful writes per minute are needed. The code is working super reliable even during peak times.
Node.js 0.8 has fs.appendFile:
fs.appendFile('message.txt', 'data to append', (err) => {
if (err) throw err;
console.log('The "data to append" was appended to file!');
});
Documentation
Using fs.appendFile or fsPromises.appendFile are the fastest and the most robust options when you need to append something to a file.
In contrast to some of the answers suggested, if the file path is supplied to the appendFile function, It actually closes by itself. Only when you pass in a filehandle that you get by something like fs.open() you have to take care of closing it.
I tried it with over 50,000 lines in a file.
Examples :
(async () => {
// using appendFile.
const fsp = require('fs').promises;
await fsp.appendFile(
'/path/to/file', '\r\nHello world.'
);
// using apickfs; handles error and edge cases better.
const apickFileStorage = require('apickfs');
await apickFileStorage.writeLines(
'/path/to/directory/', 'filename', 'Hello world.'
);
})();
Ref: https://github.com/nodejs/node/issues/7560
If you want an easy and stress-free way to write logs line by line in a file, then I recommend fs-extra:
const os = require('os');
const fs = require('fs-extra');
const file = 'logfile.txt';
const options = {flag: 'a'};
async function writeToFile(text) {
await fs.outputFile(file, `${text}${os.EOL}`, options);
}
writeToFile('First line');
writeToFile('Second line');
writeToFile('Third line');
writeToFile('Fourth line');
writeToFile('Fifth line');
Tested with Node v8.9.4.
fd = fs.openSync(path.join(process.cwd(), 'log.txt'), 'a')
fs.writeSync(fd, 'contents to append')
fs.closeSync(fd)
I offer this suggestion only because control over open flags is sometimes useful, for example, you may want to truncate it an existing file first and then append a series of writes to it - in which case use the 'w' flag when opening the file and don't close it until all the writes are done. Of course appendFile may be what you're after :-)
fs.open('log.txt', 'a', function(err, log) {
if (err) throw err;
fs.writeFile(log, 'Hello Node', function (err) {
if (err) throw err;
fs.close(log, function(err) {
if (err) throw err;
console.log('It\'s saved!');
});
});
});
Using jfile package :
myFile.text+='\nThis is new line to be appended'; //myFile=new JFile(path);
Try to use flags: 'a' to append data to a file
var stream = fs.createWriteStream("udp-stream.log", {'flags': 'a'});
stream.once('open', function(fd) {
stream.write(msg+"\r\n");
});
Here's a full script. Fill in your file names and run it and it should work!
Here's a video tutorial on the logic behind the script.
var fs = require('fs');
function ReadAppend(file, appendFile){
fs.readFile(appendFile, function (err, data) {
if (err) throw err;
console.log('File was read');
fs.appendFile(file, data, function (err) {
if (err) throw err;
console.log('The "data to append" was appended to file!');
});
});
}
// edit this with your file names
file = 'name_of_main_file.csv';
appendFile = 'name_of_second_file_to_combine.csv';
ReadAppend(file, appendFile);
const inovioLogger = (logger = "") => {
const log_file = fs.createWriteStream(__dirname + `/../../inoviopay-${new Date().toISOString().slice(0, 10)}.log`, { flags: 'a' });
const log_stdout = process.stdout;
log_file.write(logger + '\n');
}
In addition to denysonique's answer, sometimes asynchronous type of appendFile and other async methods in NodeJS are used where promise returns instead of callback passing. To do it you need to wrap the function with promisify HOF or import async functions from promises namespace:
const { appendFile } = require('fs').promises;
await appendFile('path/to/file/to/append', dataToAppend, optionalOptions);
I hope it'll help 😉
I wrapped the async fs.appendFile into a Promise-based function. Hope it helps others to see how this would work.
append (path, name, data) {
return new Promise(async (resolve, reject) => {
try {
fs.appendFile((path + name), data, async (err) => {
if (!err) {
return resolve((path + name));
} else {
return reject(err);
}
});
} catch (err) {
return reject(err);
}
});
}