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hadd.C File Reference

Detailed Description

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Macro to add histogram files This macro is kept for didactical purposes only: use instead the executable $ROOTSYS/bin/hadd !

This macro will add histograms from a list of root files and write them to a target root file. The target file is newly created and must not be identical to one of the source files. This code is based on the hadd.C example by Rene Brun and Dirk Geppert, which had a problem with directories more than one level deep. The macro from Sven has been enhanced by Anne-Sylvie Nicollerat Anne-.nosp@m.Sylv.nosp@m.ie.Ni.nosp@m.coll.nosp@m.erat@.nosp@m.cern.nosp@m..ch to automatically add Trees (via a chain of trees).

#include <string.h>
#include "TChain.h"
#include "TFile.h"
#include "TH1.h"
#include "TTree.h"
#include "TKey.h"
#include "Riostream.h"
TList *FileList;
TFile *Target;
void MergeRootfile( TDirectory *target, TList *sourcelist );
void hadd() {
// Prepare the files to me merged
if(gSystem->AccessPathName("hsimple1.root")) {
gSystem->CopyFile("hsimple.root", "hsimple1.root");
gSystem->CopyFile("hsimple.root", "hsimple2.root");
// in an interactive ROOT session, edit the file names
// Target and FileList, then
// root > .L hadd.C
// root > hadd()
Target = TFile::Open( "result.root", "RECREATE" );
FileList = new TList();
FileList->Add( TFile::Open("hsimple1.root") );
FileList->Add( TFile::Open("hsimple2.root") );
MergeRootfile( Target, FileList );
void MergeRootfile( TDirectory *target, TList *sourcelist ) {
// cout << "Target path: " << target->GetPath() << endl;
TString path( (char*)strstr( target->GetPath(), ":" ) );
path.Remove( 0, 2 );
TFile *first_source = (TFile*)sourcelist->First();
first_source->cd( path );
TDirectory *current_sourcedir = gDirectory;
//gain time, do not add the objects in the list in memory
// loop over all keys in this directory
TChain *globChain = 0;
TIter nextkey( current_sourcedir->GetListOfKeys() );
TKey *key, *oldkey=0;
while ( (key = (TKey*)nextkey())) {
//keep only the highest cycle number for each key
if (oldkey && !strcmp(oldkey->GetName(),key->GetName())) continue;
// read object from first source file
first_source->cd( path );
TObject *obj = key->ReadObj();
if ( obj->IsA()->InheritsFrom( TH1::Class() ) ) {
// descendant of TH1 -> merge it
// cout << "Merging histogram " << obj->GetName() << endl;
TH1 *h1 = (TH1*)obj;
// loop over all source files and add the content of the
// correspondant histogram to the one pointed to by "h1"
TFile *nextsource = (TFile*)sourcelist->After( first_source );
while ( nextsource ) {
// make sure we are at the correct directory level by cd'ing to path
nextsource->cd( path );
TKey *key2 = (TKey*)gDirectory->GetListOfKeys()->FindObject(h1->GetName());
if (key2) {
TH1 *h2 = (TH1*)key2->ReadObj();
h1->Add( h2 );
delete h2;
nextsource = (TFile*)sourcelist->After( nextsource );
else if ( obj->IsA()->InheritsFrom( TTree::Class() ) ) {
// loop over all source files create a chain of Trees "globChain"
const char* obj_name= obj->GetName();
globChain = new TChain(obj_name);
TFile *nextsource = (TFile*)sourcelist->After( first_source );
// const char* file_name = nextsource->GetName();
// cout << "file name " << file_name << endl;
while ( nextsource ) {
nextsource = (TFile*)sourcelist->After( nextsource );
} else if ( obj->IsA()->InheritsFrom( TDirectory::Class() ) ) {
// it's a subdirectory
cout << "Found subdirectory " << obj->GetName() << endl;
// create a new subdir of same name and title in the target file
TDirectory *newdir = target->mkdir( obj->GetName(), obj->GetTitle() );
// newdir is now the starting point of another round of merging
// newdir still knows its depth within the target file via
// GetPath(), so we can still figure out where we are in the recursion
MergeRootfile( newdir, sourcelist );
} else {
// object is of no type that we know or can handle
cout << "Unknown object type, name: "
<< obj->GetName() << " title: " << obj->GetTitle() << endl;
// now write the merged histogram (which is "in" obj) to the target file
// note that this will just store obj in the current directory level,
// which is not persistent until the complete directory itself is stored
// by "target->Write()" below
if ( obj ) {
//!!if the object is a tree, it is stored in globChain...
if(obj->IsA()->InheritsFrom( TTree::Class() ))
obj->Write( key->GetName() );
} // while ( ( TKey *key = (TKey*)nextkey() ) )
// save modifications to target file
bool Bool_t
Definition: RtypesCore.h:63
const Bool_t kFALSE
Definition: RtypesCore.h:101
const Bool_t kTRUE
Definition: RtypesCore.h:100
#define gDirectory
Definition: TDirectory.h:384
Option_t Option_t TPoint TPoint const char GetTextMagnitude GetFillStyle GetLineColor GetLineWidth GetMarkerStyle GetTextAlign GetTextColor GetTextSize void char Point_t Rectangle_t WindowAttributes_t Float_t Float_t Float_t Int_t Int_t UInt_t UInt_t Rectangle_t Int_t Int_t Window_t TString Int_t GCValues_t GetPrimarySelectionOwner GetDisplay GetScreen GetColormap GetNativeEvent const char const char dpyName wid window const char font_name cursor keysym reg const char only_if_exist regb h Point_t winding char text const char depth char const char Int_t count const char ColorStruct_t color const char Pixmap_t Pixmap_t PictureAttributes_t attr const char char ret_data h unsigned char height h Atom_t Int_t ULong_t ULong_t unsigned char prop_list Atom_t Atom_t target
R__EXTERN TSystem * gSystem
Definition: TSystem.h:560
A chain is a collection of files containing TTree objects.
Definition: TChain.h:33
virtual Long64_t Merge(const char *name, Option_t *option="")
Merge all the entries in the chain into a new tree in a new file.
Definition: TChain.cxx:1892
virtual Int_t Add(TChain *chain)
Add all files referenced by the passed chain to this chain.
Definition: TChain.cxx:218
Bool_t InheritsFrom(const char *cl) const override
Return kTRUE if this class inherits from a class with name "classname".
Definition: TClass.cxx:4863
Bool_t cd() override
Change current directory to "this" directory.
Describe directory structure in memory.
Definition: TDirectory.h:45
static TClass * Class()
virtual TList * GetListOfKeys() const
Definition: TDirectory.h:223
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format.
Definition: TFile.h:54
static TFile * Open(const char *name, Option_t *option="", const char *ftitle="", Int_t compress=ROOT::RCompressionSetting::EDefaults::kUseCompiledDefault, Int_t netopt=0)
Create / open a file.
Definition: TFile.cxx:4053
TH1 is the base class of all histogram classes in ROOT.
Definition: TH1.h:58
static TClass * Class()
static void AddDirectory(Bool_t add=kTRUE)
Sets the flag controlling the automatic add of histograms in memory.
Definition: TH1.cxx:1267
virtual Bool_t Add(TF1 *h1, Double_t c1=1, Option_t *option="")
Performs the operation: this = this + c1*f1 if errors are defined (see TH1::Sumw2),...
Definition: TH1.cxx:807
static Bool_t AddDirectoryStatus()
Static function: cannot be inlined on Windows/NT.
Definition: TH1.cxx:735
Book space in a file, create I/O buffers, to fill them, (un)compress them.
Definition: TKey.h:28
virtual TObject * ReadObj()
To read a TObject* from the file.
Definition: TKey.cxx:750
A doubly linked list.
Definition: TList.h:38
TObject * After(const TObject *obj) const override
Returns the object after object obj.
Definition: TList.cxx:330
void Add(TObject *obj) override
Definition: TList.h:81
TObject * First() const override
Return the first object in the list. Returns 0 when list is empty.
Definition: TList.cxx:659
const char * GetName() const override
Returns name of object.
Definition: TNamed.h:47
Mother of all ROOT objects.
Definition: TObject.h:41
virtual const char * GetName() const
Returns name of object.
Definition: TObject.cxx:439
virtual Int_t Write(const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
Write this object to the current directory.
Definition: TObject.cxx:874
virtual const char * GetTitle() const
Returns title of object.
Definition: TObject.cxx:483
virtual TClass * IsA() const
Definition: TObject.h:245
Basic string class.
Definition: TString.h:136
virtual int CopyFile(const char *from, const char *to, Bool_t overwrite=kFALSE)
Copy a file.
Definition: TSystem.cxx:1344
virtual Bool_t AccessPathName(const char *path, EAccessMode mode=kFileExists)
Returns FALSE if one can access a file using the specified access mode.
Definition: TSystem.cxx:1299
static TClass * Class()
TH1F * h1
Definition: legend1.C:5
Sven A. Schmidt, sven..nosp@m.schm.nosp@m.idt@c.nosp@m.ern..nosp@m.ch, 13.2.2001

Definition in file hadd.C.