Method opened

source/matplot/util/popen.h:49–49

    FILE *file() const { return file_; }
    int close(int *exit_code = nullptr);
    bool opened() const { return file_ != nullptr; }
    const std::string& error() const { return error_; }
    bool exceptions() const { return exceptions_; }
    void exceptions(bool exc) { exceptions_ = exc; }