Dear experts,
When I try to merge root files with the same structure using $ROOTSYS/bin/hadd I get the following response:
hadd Opening the next 77 files. No idea what does it mean. But the size of merged file is less than I would expect. Therefore I suspect that not all files are merged. Using ROOT 6.06/00.
Please help.
Best regards
Yuri
Dear Yuri,
How many files are you trying to merge?
Does it work if you merge 2 or a small number of files?
On what is your expected merged file size based?
G Ganis
Dear Ganis,
I encountered it first when I tried to merge 1000 files.
With the file size everything seems to be ok, after I have checked the average number of events per file.
That means all files were merged.
Still puzzled what means 77 files. 
Yuri
Dear Yuri,
So, if I understand correctly, the result is not anymore wrong or unexpected.
The only problem is the message, which is a verbosity message normally printed if you run hadd in verbose mode, i.e. with the switch ‘-v [verbosity]’: is this your case?
G Ganis
Dear Ganis,
Yes the result seems to be as expected.
I do not run hadd with the switch -v but simply like hadd outputfile inputfiles.
Yuri
Dear Yuri,
Ok, good to read that the result is ok.
The verbosity is actually on by default, so the message is normal when merging a large number of files.
Passing ‘-v 0’ should silence it.
G Ganis