From GridLAB-D Wiki
The verbose option produces all but the debugging output from GridLAB-D. It is managed by the global variable verbose, which is by default FALSE.
GLM
To enable verbose mode use the directive
#set verbose=1
To disable verbose mode use the directive
#set verbose=0
Command line
To toggle verbose mode use the option
host% gridlabd --verbose
To enable verbose mode use the option
host% gridlabd -D verbose=1
To disable verbose mode use the option
host% gridlabd -D verbose=0