labels -- Display list of defined labels
p4 labels [ file[revrange] ]
Reports the list of all labels currently known to the system.
If files are specified, 'p4 labels' limits its report to labels
that contain those files. If the file specification includes
a revision range, 'p4 labels' limits its report to labels that
contain those particular revisions. See 'p4 help revisions'
for help specify revisions.