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hadd - Man Page


usage: hadd [-a] [-f] [-f[0-9]] [-fk] [-ff] [-k] [-O] [-T] [-v V] [-j J]
           [-dbg] [-d D] [-n N] [-cachesize CACHESIZE]
           [-experimental-io-features EXPERIMENTAL_IO_FEATURES]


This program will add histograms, trees and other objects from a list of ROOT files and write them to a target ROOT file. The target file is newly created and must not exist, or if -f ("force") is given, must not be one of the source files.



Append to the output


Force overwriting of output file


Gives the ability to specify the compression level of the target file.

Default is 1 (kDefaultZLIB), 0 is uncompressed, 9 is maximum

compression (see TFile::TFile documentation). You can also specify the

full compresion algorithm, e.g. -f206


Sets the target file to contain the baskets with the same compression

as the input files (unless -O is specified). Compresses the meta data

using the compression level specified in the first input or the

compression setting after fk (for example 206 when using -fk206)


The compression level use is the one specified in the first input


Skip corrupt or non-existent files, do not exit


Re-optimize basket size when merging TTree


Do not merge Trees


Explicitly set the verbosity level: 0 request no output, 99 is the



Parallelize the execution in 'J' processes. If the number of processes

is not specified, use the system maximum.


Enable verbosity. If -j was specified, do not not delete partial files

stored inside working directory.


Carry out the partial multiprocess execution in the specified



Open at most 'N' files at once (use 0 to request to use the system



Resize the prefetching cache use to speed up I/O operations (use 0 to



Used with an argument provided, enables the corresponding experimental

feature for output trees. See ROOT::Experimental::EIOFeatures


Target file


Source files