Emscripten default working environment

EmscriptenEnv.md

Default Environment variable

        ENV['USER'] = ENV['LOGNAME'] = 'web_user';
        ENV['PATH'] = '/';
        ENV['PWD'] = '/';
        ENV['HOME'] = '/home/web_user';
        ENV['LANG'] = 'C.UTF-8';
        ENV['_'] = Module['thisProgram'];

File System (/dev, /proc,... )

        FS.mkdir('/tmp');
        FS.mkdir('/home');
        FS.mkdir('/home/web_user');
        FS.mkdir('/dev');
        FS.mkdev('/dev/null', FS.makedev(1, 3));
        /dev/tty
        /dev/tty1
        FS.createDevice('/dev', 'random', random_device);
        FS.createDevice('/dev', 'urandom', random_device);
        // we're not going to emulate the actual shm device,
        // just create the tmp dirs that reside in it commonly
        FS.mkdir('/dev/shm');
        FS.mkdir('/dev/shm/tmp');
        FS.mkdir('/proc');
        FS.mkdir('/proc/self');
        FS.mkdir('/proc/self/fd');

        if (Module['stdin']) {
          FS.createDevice('/dev', 'stdin', Module['stdin']);
        } else {
          FS.symlink('/dev/tty', '/dev/stdin');
        }
        if (Module['stdout']) {
          FS.createDevice('/dev', 'stdout', null, Module['stdout']);
        } else {
          FS.symlink('/dev/tty', '/dev/stdout');
        }
        if (Module['stderr']) {
          FS.createDevice('/dev', 'stderr', null, Module['stderr']);
        } else {
          FS.symlink('/dev/tty1', '/dev/stderr');
        }
  
        // open default streams for the stdin, stdout and stderr devices
        var stdin = FS.open('/dev/stdin', 'r');
        var stdout = FS.open('/dev/stdout', 'w');
        var stderr = FS.open('/dev/stderr', 'w');