How to Efficiently Merge ROOT Files in Multiple Directories?

[ChrisVer]

Suppose I have a collection of 40 directories, each containing 1, 2 ,3 ,4 or 5 .root files with histograms and trees.
What is an optimal way to merge those .root files so I would end up with 40 directories and 40 root files with the histos added together?
One way I thought of was to start typing for the 40 different directories an "hadd" command in the terminal.

"hadd sum1.root dir1/*.root"
"hadd sum2.root dir2/*.root"
...
"hadd sum40.root dir40/*.root"

However I find this kind of tiring and stupid. Do you have any better solution?
My problem with a macro is that I am not sure if it understands the *.root notation (so I cannot think of iterating).
Finally I am not sure if a TChain can, apart from Trees in different root files, merge TH1s (histograms) too.

THanks :)

 

[andrewkirk]

You could write a shell script that uses iteration to generate a text file containing a single line of the form:

hadd sum1.root dir1/*.root & ; hadd sum1.root dir2/*.root & ; hadd sum3.root dir1/*.root & ; ... ; hadd sum1.root dir40/*.root​

then just copy the line to the command prompt and execute it

 

[ChrisVer]

You could write a shell script that uses iteration to generate a text file containing a single line of the form:

hadd sum1.root dir1/*.root & ; hadd sum1.root dir2/*.root & ; hadd sum3.root dir1/*.root & ; ... ; hadd sum1.root dir40/*.root​

then just copy the line to the command prompt and execute it

Thanks for the reply...
It helped me to try to do it manually... after the 3rd try, I figured out what "for loop" I had to use in the shell script...That's what I had to do:

i=0
for folder in directory_path_of_folders/*; do
    hadd -f target_directory/sumfile$((i++)).root $folder/*.root
done