Shell Programming and Scripting

! comment
command d
command b
command c
! 
interface b
   podcommand b
   podcommand a
!
interface a
   podcommand b
   podcommand a
! 
command a

command a
command b
command c
command d
interface a
   podcommand a
   podcommand b
interface b
   podcommand a
   podcommand b

awk '/!/{next} !/^ +/ {S=$0; print; next} {$0=S " " $0} 1' file | sort | awk 'NF>2 {$1=$2=""}1'
command a
command b
command c
command d
interface a
  podcommand a
  podcommand b
interface b
  podcommand a
  podcommand b

awk '/!/{next} !/^[^A-Za-z0-9 ]+/ {S=$0; print; next} {$0=S " " $0} 1' file | sort | awk '
BEGIN { prefix="test" } 
{  
if ( match($0, prefix) && length($0)>0 ) 
{ sub(prefix, "", $0) } 
else if ( length($0)>0 ) 
{ prefix=$0  } 
print $0  
}'