Notes on using LIGOtools packages which are based on ROOT

Certain LIGOtools packages, such as dmtroot and eventtool, consist of code which can be loaded into ROOT and executed in an interactive or scripted session. The LIGOtools root package consists of a version of ROOT (ltroot) which has been slightly modified so that when it starts up, it automatically loads the appropriate shared-object libraries and macros for all ROOT-based LIGOtools packages. (Technical detail: this is done using a shell script which checks for the existence of "Logon" macros in $LIGOTOOLS/root for each LIGOtools package, then tells ROOT to execute these as it starts up.)

There are two things you need to keep in mind to be able to use ROOT-based LIGOtools packages successfully:

• If there is a .rootrc file in your home directory, or in the current working directory when you start up ROOT, then it must specify a value of Unix.*.Root.MacroPath which includes the $LIGOTOOLS/root directory. To dereference an environment variable in a .rootrc file, enclose it in parentheses, e.g.:

  Unix.*.Root.MacroPath:      .:$(LIGOTOOLS)/root:$(ROOTSYS)/macros
  

  If you do not have your own .rootrc file, don't worry; the default Unix.*.Root.MacroPath for the LIGOtools version of root includes $(LIGOTOOLS)/root, as shown above.

• Beginning with version 3.02.07a of the LIGOtools root package, you must type ltroot, rather than just root, to start up the LIGOtools version of ROOT. (Previously, typing root would also start up the LIGOtools version of ROOT, but only if there were not another copy of ROOT that appeared earlier in your PATH.)