LARDON reads three environment variables at startup. If any variable is unset, LARDON falls back to os.getcwd() — the directory from which the lardon command was invoked.
| Variable | Purpose | Default if unset |
|---|
LARDON_PATH | Path to the src/lardon/ directory (settings, channel maps, calibration files) | os.getcwd() |
LARDON_RECO | Directory where reconstructed HDF5 output files are written | os.getcwd() |
LARDON_PLOT | Directory where control plots are saved | os.getcwd() |
Setting environment variables with set_lardon.sh
The repository ships with set_lardon.sh in its root directory. Source it once per shell session before running LARDON:
The script sets all three variables relative to $PWD, so run it from the repository root:
#!/bin/bash
export QT_XCB_GL_INTEGRATION=none
#eval "$(pixi shell-hook)"
#uncomment next two lines to open files outside of CERN/FERMILAB
#xrootd=$(find .pixi -name "libXrdPosixPreload.so")
#export LD_PRELOAD=$PWD/$xrootd
export LARDON_PATH=$PWD/src/lardon
export LARDON_RECO=$PWD/reco
export LARDON_PLOT=$PWD/plots
echo $LARDON_PATH # .../lardon/src/lardon
echo $LARDON_RECO # .../lardon/reco
echo $LARDON_PLOT # .../lardon/plots
set_lardon.sh sets LARDON_RECO to $PWD/reco and LARDON_PLOT to $PWD/plots. These directories are not created automatically — create them if they do not exist:Setting variables manually
You can also export the variables directly for non-standard layouts:
export LARDON_PATH=/path/to/lardon/src/lardon
export LARDON_RECO=/scratch/my_project/reco
export LARDON_PLOT=/scratch/my_project/plots
How LARDON uses the variables
The variables are read in src/lardon/config.py:
lardon_path = os.environ.get("LARDON_PATH", os.getcwd())
store_path = os.environ.get("LARDON_RECO", os.getcwd())
plot_path = os.environ.get("LARDON_PLOT", os.getcwd())
LARDON_PATH is the most critical: LARDON constructs all internal paths from it, including the path to detector settings ($LARDON_PATH/settings/), channel maps, and calibration files. If it is wrong, LARDON will fail to load detector geometry and abort.
Qt headless display
set_lardon.sh also exports:
export QT_XCB_GL_INTEGRATION=none
XRootD for remote file access
If you need to open raw data files stored outside CERN or Fermilab — for example, using the -file root://... command-line option — uncomment the two XRootD lines in set_lardon.sh:
xrootd=$(find .pixi -name "libXrdPosixPreload.so")
export LD_PRELOAD=$PWD/$xrootd
LD_PRELOAD affects all child processes started in the same shell session. If you encounter unexpected crashes in unrelated tools after sourcing the script, comment the XRootD lines out again.
