https://youtu.be/tdn8ubicWsY

youtube-dl commands look like this (but the name of the video is an incremented integer— 1.mp4, 2.mp4, etc):

youtube-dl -f worstvideo --max-downloads 5 -o /Users/a/Documents/of_v0.9.8_osx_release/apps/myApps/20180318_detourningTheWeb_assignment3/bin/data/vids_sky/1.mp4 "https://www.youtube.com/results?sp=CAISAhgB&search_query=sky+timelapse"

youtube-dl -f worstvideo --max-downloads 5 -o /Users/a/Documents/of_v0.9.8_osx_release/apps/myApps/20180318_detourningTheWeb_assignment3/bin/data/vids_grass/1.mp4 "https://www.youtube.com/results?search_query=grass+timelapse&sp=CAISAhgB"

 

I called this shell command from within my oF app with a `system()` call from a separate thread (created with the `fork()` function):

void ofApp::downloadVid(int vidType, bool _isVidDownloaded, string dir, string vidUrl, string vidId){
    if(!_isVidDownloaded){
        if(!forkOnce_downloadVid){
            string vidName = "/Users/a/Documents/of_v0.9.8_osx_release/apps/myApps/20180318_detourningTheWeb_assignment3/bin/data/" + dir + vidId + ".mp4";
            
            cout << "vidName = " << vidName << endl;
            
            //youtube-dl -f worstvideo --max-downloads 5 -o /Users/a/Documents/of_v0.9.8_osx_release/apps/myApps/20180318_detourningTheWeb_assignment3/bin/data/vids/sky.mp4 "https://www.youtube.com/results?sp=CAISAhgB&search_query=sky+timelapse"
            
            string cmd = "/usr/local/bin/youtube-dl -f worstvideo --max-downloads 1 --playlist-start " + vidId + " --recode-video mp4 -o " + vidName + " "" + vidUrl.c_str() + """;
            
            cout << "cmd = " << cmd << endl;
            
            int pid = fork();
            switch(pid){
                case -1:{
                    perror("fork");
                    _exit(EXIT_FAILURE);
                    break;
                }
                case 0:{ // child process
                    system(cmd.c_str());
                    _exit(0);
                    break;
                }
                default:{ // parent process
                    // wait for child process
                    int status = 0;
                    waitpid(-1, &status, WNOHANG);
                    printf("child status:%dn",status);
                    break;
                }
            }
            forkOnce_downloadVid = true;
        } else {
            if(vidType == 0) {
                signal(SIGCHLD,signalHandler_sky);
            } else {
                signal(SIGCHLD,signalHandler_grass);
            }
        }
        
    }
}