var fp = 'ffprobe ' + fileName + ' -show_streams | grep '
var width = exec(fp+'width', function(err, stdout, stderr){
    return stdout;
});
alert(stdout + 'random example');

how do I get the stdout 'out' of the process so that I can use it later.

var fp = 'ffprobe ' + fileName + ' -show_streams | grep '
var width = exec(fp+'width', function(err, stdout, stderr){
    return stdout;
});
alert(stdout + 'random example');

how do I get the stdout 'out' of the process so that I can use it later.

• javascript
• node.js

4 Answers 4

Node's exec function is asynchronous. This means that there is no guarantee that code below the exec call will wait until the child process finishes to run. To execute code once the process quits, then, you must provide a callback which deals with the results. Your code can branch off from there:

var fp = 'ffprobe ' + fileName + ' -show_streams | grep ';
var width = exec(fp+'width', function(err, stdout, stderr){
    console.log(stdout);

    // ... process stdout a bit ...

    afterFFProbe(stdout);
});

function afterFFProbe(output) {
    // your program continues here
}

None of the answers above worked for me. This did though.

var probeCommand = 'rtsp://xx.xx.xx.xx/axis-media/media.3gp'
exec('ffprobe '+probeCommand+' | echo ',function(err,stdout,stderr){
    console.log(stdout+stderr)
})

If I'm understanding you correctly:

var fp = 'ffprobe ' + fileName + ' -show_streams | grep ',
    value,
    width = exec(fp+'width', function(err, stdout, stderr) {
        value = stdout;
        return stdout;
    });
alert(value + 'random example');

I think this might work:

var output = "";
var fp = 'ffprobe ' + fileName + ' -show_streams | grep '
var width = exec(fp+'width', function(err, stdout, stderr){
this.output = stdout;
});
alert(output + 'random example');