Useful Parameters

Evnironment Variables

The behaviour of ROOT can be steered with the usage of environment variables. The table below, summarises their names, types and purpose.

Name	Type or Value	Description
JSROOTSYS	path	Location of JSROOT. Used for notebooks integration, RWebDisplayHandle and THttpServer.
ROOT_BATCH	-	If defined, enable ROOT’s batch mode
ROOT_DISABLE_TCLASS_GET_CLASS_AUTOPARSING	-	if defined, disable auto-parsing
ROOT_EXPERIMENTAL_EXPORT_RNTUPLE_METRICS	path	Location of RNTuple’s exported metrics
ROOT_HIST	string	Of the form “N1:N2”, N1 and N2 are integers. N1: maximum number of lines to be kept in the .roothist file; N2 (optional): once the lines saved are N1, the last N2 lines will be removed
ROOT_LISTENER_SOCKET	path	Location of the unix socket for remote connections
ROOT_MAX_THREADS	unsigned int	Cap the size of the implicit multi threading thread pool
ROOT_OBJECT_AUTO_REGISTRATION	bool	Set ROOT7 mode for object auto registration
ROOT_RNTUPLE_CLUSTERBUNCHSIZE	int	Set the number of clusters the reader should prefetch or queue up at once
ROOT_TTREECACHE_PREFILL	bool	Set ttree cache filling by reading all branch baskets at entry 0
ROOT_WEBDISPLAY	off/batch/native/chromechromium/firefox/edge/server/qt6…	Set backend for web-graphics windows’ handling. At the command line that would be specified with the switch --web=XYZ
ROOT_WEBGUI_SOCKET	url or path	Set socket, e.g. TCP or Linux, for the internal web-graphics server
ROOTDEBUG	1,2,3,4	Set verbosity level, the higher the more verbose
ROOTENV_NO_HOME	-	If defined, ignore .rootrc file in the home directory
ROOTENV_USER_PATH	path	If defined, location of .rootrc instead of the one in the home directory
ROOTIGNOREPREFIX	bool	If true, force ROOT to use the $ROOTSYS path instead of a hardcoded, system-wide installation prefix
ROOTSYS	path	Location of ROOT’s build or install directory (being abandoned)
ROOTUI5SYS	path	If defined, location of ui5