Read histogram from TFile while actively writing to it (with example)

ROOT
4

I modified my script to call TFile::Open(), instead of taking a pointer to a TFile. It’s a modification from this post. According to Philippe, this is not the most efficient way to do this, see here.

Thus far this is the most robust method I’ve found.

#include <TFile.h>
#include <TH1.h>

#include <iostream>

void viewOnline(const std::string &filename, const int &id) {
    const char *name = ("h"+std::to_string(id)).c_str();
    TFile *file = TFile::Open(filename.c_str());
    TH1D *hist1;
    file->GetObject(name, hist1);
    hist1->Draw();
}