In nodejs how to read a file and move it to another folder if the file contains a specified text

Question

So I have the following code

var processed;
fs.readFile(path, 'utf-8', function(err, data) {
    processed = false;
    //checking if text is in file and setting flag
    processed = true;
});

if (processed == true) {
    try {
        var fname = path.substring(path.lastIndexOf("\\") + 1);
        fs.moveSync(path, './processedxml/' + fname, {
            overwrite: true
        })
    } catch (err) {
        console.log("Error while moving file to processed folder " + err);
    }

}

But I don't get the desired output. Because looks like the readfile is executed by a separate thread and so the value of "processed" is not reliable.

I am not very familiar with nodejs so any help will be greatly appreciated.

Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Marcos Casagrande, May 01 '18 at 17:15
There is also a synchronous version: https://nodejs.org/api/fs.html#fs_fs_readfilesync_path_options `fs.readFileSync(path, options)` — Matthias Herrmann, May 01 '18 at 17:17
Simply move your code into the function rather than setting a flag. — Jake Holzinger, May 01 '18 at 18:08
The `fs.readFile` callback is called after the file is read, not while the file is open, there is likely another issue, perhaps you're trying to move the file to a folder that does not exist. — Jake Holzinger, May 01 '18 at 18:29
@Jake : ohh ok...but how do I get the value of path in the callback — Aparna, May 02 '18 at 12:56
It looks like you're shadowing the `path` variable. I posted an answer. — Jake Holzinger, May 02 '18 at 13:58

score 0 · Answer 1 · answered May 01 '18 at 18:48

Yes, you are right, your executions are performed by different threads.

In this scenario, you'll need to use promises.

You can solve your need easily by using "Promise FS" (you can use any other promise solution anyway).

Your code would be something like the following:

fs = require('promise-fs');

var fname = 'test.txt' ;
var toMove = false ;

fs.readFile('test.txt','utf8')
    .then (function (content) {
        if(content.indexOf('is VALID') !== -1) {
            console.log('pattern found!');
            toMove = true ;
        }
        else { toMove = false
        }
        return toMove ;
    }).
    then (function (toMove) {
           if(toMove) {
              var oldPath = 'test.txt'
              var newPath = '/tmp/moved/file.txt'
              fs.rename(oldPath, newPath, function (err) {
                if (err) throw err
                console.log('Successfully renamed - moved!')
              }) ;
           }
    })
    .catch (function (err) {
        console.log(err);
    })

Create a file "test.txt" and add the following contents:

this is text.file contents
token is VALID

The code above will evaluate if "is VALID" is present as content and if it does then it will move the file "test.txt" from your current folder to a new one called "moved" in "/tmp" directory. It will also rename the file as "file.txt" file name.

Hope it helps you.

Regards

score 0 · Answer 2 · answered May 02 '18 at 13:58

It looks like you're shadowing path, trying to use it as a variable and as a node module. The easiest way to make this work is to choose a different variable name for the file and move the processing logic into the callback of fs.readFile.

var path = require('path');
var fs = require('fs-extra');

var file = 'some/file/path/foo.xml';
var text = 'search text';

fs.readFile(file, 'utf-8', function (err, data) {
    if (err) {
        console.error(err);
    } else {
        //checking if text is in file and setting flag
        if (data.indexOf(text) > -1) {
            try {
                var fname = path.basename(file);
                fs.moveSync(file, './processedxml/' + fname, {
                    overwrite: true
                })
            } catch (err) {
                console.log("Error while moving file to processed folder " + err);
            }
        }
    }
});

In nodejs how to read a file and move it to another folder if the file contains a specified text

2 Answers2