if (stdout=="E") always return false

Question

if (stdout=="E") always return false

I m comparing the output of childprocess.exec to a tring, but I must overlook something since I don t get the expected result.

function download_all(list, callback){
    var i=0, cmd="";

    function afterDownload(){...}

    while(i<list.length)
    {
        cmd="[ -f ./downloads/"+list[i]+" ] && echo \"E\" || echo\""+list[i]+"\"";
        exec(cmd, function(error, stdout, stderr){
            if(stdout=="E")
            {
                console.log("Already Exist");
            }else{
                console.log("download "+LINK+""+stdout);
                download(LINK+stdout, afterDownload());
            }
        });
        i=i+1;
    }

Basically, I check if a file exist, look at the output of the command, and if it is not E (wich sign the file exist), download it. The problem is, even when the file exist, the app try to download LINK+E, wich doesn t exist and of course fail.

I ve tried with === instead of ==, and " instead of ', but it didn t changed anything.

Is there some character in stdout other than E?

javascript
node.js
bash

Answer 1

NodeJS has the "fs" module which takes care of that for you. The documentation is at http://nodejs.org/api/fs.html

You can do this:

fs.exists(list[i], function (exists) {
  console.log("exists = ", exists);
});