How to count number of paths in RTL-compiler group?

 Thanks for answer Johannes,

 This solution works. And do you have an idea how to detect if path group empty or not in tcl script? Let me clarify my problem a little:

 I automatically create cost groups between all clocks in design in script. If there are 2 clocks in design my script will create following cost groups:

    inputs_2_clk1, clk1_to_clk1,clk1_to_outputs, clk1_to_clk2,

    inputs_2_ clk2, clk2_to_clk2,clk2_to_outputs, clk2_to_clk1

Althougth some groups are empty RTL compiler creates them. I suppose that this leads to memory usage increase and dramatically increase final output *.sdc file. So, I want to find a way to delete or not to create empty cost groups before synthesis starts...I have a feeling that I need to use linux 'grep' command on results of rc 'report timing -paths [eval [get_attribute paths <path-group name>]]' command, but I don't know how... 

Thank, dkos 

 P.S. script that I use for cost group creation:

#delete cost groups, created by create_clock commands
puts "----------------------------------------------------------------------------"
puts "Delete cost groups, created by create_clock commands and add own cost_groups"
puts "----------------------------------------------------------------------------"
rm [find / -cost *]

set CLOCK_LIST [find / -clock *]
#collect registers for all clocks
set i 0
foreach clock ${CLOCK_LIST} {
  set clock [basename $clock]
  puts "-- collect all regs for clock: ${clock}"
 
  set regs_of_clock($i) [all des seqs -clock ${clock}]
  set regs_col_clock [llength $regs_of_clock($i)]
  puts "-- number of regs: ${regs_col_clock}"
  incr i
}
  set clock_num [llength ${CLOCK_LIST}]
  puts "-- number of clocks: $clock_num"

#generate new cost groups
set i 0
foreach clock ${CLOCK_LIST} {
  set clock [basename $clock]
  puts "-- generate costgroups for clock: ${clock} --"
  puts "-------------------------------------------------------"

  set inList [all des inps -clock ${clock}]
  set outList [all des outs -clock ${clock}]
 
  if {[llength $regs_of_clock($i)] > 0} {
    #I2R paths
    if {[llength $inList] > 0} {
      puts "  -- generate costgroups for clock: I2${clock}"
      define_cost_group -name "I2${clock}"
      path_group -mode System -from $inList -to $regs_of_clock($i) -group I2${clock} -name I2${clock}
    }
    #R2O paths
    if {[llength $outList] > 0} {
      puts "  -- generate costgroups for clock: ${clock}2O"
      define_cost_group -name "${clock}2O"
      path_group -mode System -from $regs_of_clock($i) -to $outList -group ${clock}2O -name ${clock}2O
    }
    #R2R paths
    for {set j 0} {$j < $clock_num} {incr j} {
      set clockB [lindex ${CLOCK_LIST} $j]
      set clockB [basename $clockB]
      puts "  -- generate costgroups for clock: ${clock}->${clockB}"
   
      define_cost_group -name "${clock}2${clockB}"
      path_group -mode System -from $regs_of_clock($i) -to $regs_of_clock($j) -group ${clock}2${clockB} -name ${clock}2${clockB}
    }
  }
  incr i
}

 Thanks for answer Johannes,

 This solution works. And do you have an idea how to detect if path group empty or not in tcl script? Let me clarify my problem a little:

 I automatically create cost groups between all clocks in design in script. If there are 2 clocks in design my script will create following cost groups:

    inputs_2_clk1, clk1_to_clk1,clk1_to_outputs, clk1_to_clk2,

    inputs_2_ clk2, clk2_to_clk2,clk2_to_outputs, clk2_to_clk1

Althougth some groups are empty RTL compiler creates them. I suppose that this leads to memory usage increase and dramatically increase final output *.sdc file. So, I want to find a way to delete or not to create empty cost groups before synthesis starts...I have a feeling that I need to use linux 'grep' command on results of rc 'report timing -paths [eval [get_attribute paths <path-group name>]]' command, but I don't know how... 

Thank, dkos 

 P.S. script that I use for cost group creation:

#delete cost groups, created by create_clock commands
puts "----------------------------------------------------------------------------"
puts "Delete cost groups, created by create_clock commands and add own cost_groups"
puts "----------------------------------------------------------------------------"
rm [find / -cost *]

set CLOCK_LIST [find / -clock *]
#collect registers for all clocks
set i 0
foreach clock ${CLOCK_LIST} {
  set clock [basename $clock]
  puts "-- collect all regs for clock: ${clock}"
 
  set regs_of_clock($i) [all des seqs -clock ${clock}]
  set regs_col_clock [llength $regs_of_clock($i)]
  puts "-- number of regs: ${regs_col_clock}"
  incr i
}
  set clock_num [llength ${CLOCK_LIST}]
  puts "-- number of clocks: $clock_num"

#generate new cost groups
set i 0
foreach clock ${CLOCK_LIST} {
  set clock [basename $clock]
  puts "-- generate costgroups for clock: ${clock} --"
  puts "-------------------------------------------------------"

  set inList [all des inps -clock ${clock}]
  set outList [all des outs -clock ${clock}]
 
  if {[llength $regs_of_clock($i)] > 0} {
    #I2R paths
    if {[llength $inList] > 0} {
      puts "  -- generate costgroups for clock: I2${clock}"
      define_cost_group -name "I2${clock}"
      path_group -mode System -from $inList -to $regs_of_clock($i) -group I2${clock} -name I2${clock}
    }
    #R2O paths
    if {[llength $outList] > 0} {
      puts "  -- generate costgroups for clock: ${clock}2O"
      define_cost_group -name "${clock}2O"
      path_group -mode System -from $regs_of_clock($i) -to $outList -group ${clock}2O -name ${clock}2O
    }
    #R2R paths
    for {set j 0} {$j < $clock_num} {incr j} {
      set clockB [lindex ${CLOCK_LIST} $j]
      set clockB [basename $clockB]
      puts "  -- generate costgroups for clock: ${clock}->${clockB}"
   
      define_cost_group -name "${clock}2${clockB}"
      path_group -mode System -from $regs_of_clock($i) -to $regs_of_clock($j) -group ${clock}2${clockB} -name ${clock}2${clockB}
    }
  }
  incr i
}