Summarize start/stop times of RINEX files
 
 USAGE :  sh_get_times -f <files> -o <out-file> -sort
 
 where the input files one of the following:
   - RINEX (yy.o)
   - the output of sh_rxscan (.doc) 
   - the output of  sh_link_rinex1 (.summary)
 
   out-file is the file name for the output list (if omitted, write to screen)
 
   -sort will sort by time (otherwise by station)
 
   Examples:
 
   sh_get_times -f *.98o
   sh_get times -f *.98o -sort
   sh_get_times -f *.doc
   sh_get_times -f *.summary
   sh_get_times -f ankr*.doc
 
 where the input files one of the following:
   - RINEX (yy.o)
   - the output of sh_rxscan (.doc) 
   - the output of  sh_link_rinex1 (.summary)