fs.readFileSync Cannot read file passing path variable in nodejs

Question

I am trying to read xml file using fs.I am not able to read file using fs.readFileSync after passing path variable as first paramter to this function. Note:this is in windows machine

xmlFile="C:\Users\xyz\AppData\Local\.proxySettings.xml";
function myFunc(xmlFile) {
 let xmlData = fs.readFile(xmlFile);
 alert(xmlData);//doesn't print anything

 parser = new DOMParser();
 xmlDoc = parser.parseFromString(xmlData,"text/xml");
....
....
}

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  <proxy_port>2582</proxy_port>

update in the file

 try{
    ffile="jdkdkj";
  fs.readFileSync(ffile); 
}catch(err){
  app.console.log(err);
}

Error { errno: -4058, syscall: 'open', code: 'ENOENT', path: 'jdkdkj' }

Your code shows let xmlData = fs.readFile(xmlFile); which will never work as fs.readFile() is asynchronous and requires a callback as the second argument to communicate back the result. Also, your backslashes in the path have to be double escaped. — jfriend00
– jfriend00, Commented Jun 24, 2019 at 22:09
let io="C:\\cygwin64\\xyz\\tmp.txt"; var data=fs.readFileSync(io); alert(data); //doesn't show anything — karansys
– karansys, Commented Jun 25, 2019 at 9:41

Mark · Accepted Answer · 2019-06-24 23:05:01Z

1

In JavaScript the backslash character is used to signal that the character immediately following it should be treated specially. In order to create a literal backslash inside a JavaScript string you need to escape the backslash with another backslash.

var a = "\abc";
console.log(a); // abc
var b = "\\abc";
console.log(b); // \abc
var c = "\"abc\"";
console.log(c); // "abc"

xmlFile="C:\\Users\\xyz\\AppData\\Local\\.proxySettings.xml";
console.log(xmlFile); // C:\Users\xyz\AppData\Local\.proxySettings.xml

So, windows pathnames always need double backslashes in JavaScript

edited Jun 24, 2019 at 23:05

answered Jun 24, 2019 at 21:57

Mark

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6 Comments

karansys Over a year ago

I tried this xmlFile = xmlFile.replace(/\\/g,'\\\\'); but still it doesn't print file contents

Mark Over a year ago

You should be able to do xmlFile="C:\\Users\\xyz\\AppData\\Local\\.proxySettings.xml"; let xmlData = fs.readFile(xmlFile); Is xmlFile assigned a pathname in your code as a string literal? Or is it read from a database?

Mark Over a year ago

Then you don't need the replace(), using double backslashes should work. Let us know how it goes

karansys Over a year ago

It didn't read the file when I passed a path varaiable as first parmater to readFile or readFileSync

Mark Over a year ago

When I do fs.readFileSync("file-that-doesnt-exist") I get an exception that looks like this: { Error: ENOENT: no such file or directory, open 'foo' at Object.openSync (fs.js:443:3) at Object.readFileSync (fs.js:343:35) errno: -2, syscall: 'open', code: 'ENOENT', path: 'foo' } Are you seeing something like that?

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