Shell Programming and Scripting

Input:
*& abc def
1
2
3
4
5

*& cde efg
1
2
3

*& abc def
1
2
3
4
5

Output:
*& cde efg
1
2
3

*& abc def
1
2
3
4
5

awk 'BEGIN{RS='\n\n'};{A[$0]=1};END{for (h in A) print h,"\n"}' file

awk '/^\*\&/ {STOP=($0 in T); T[$0]} /^ *$/ {STOP=0} !STOP' file

awk '/^\*\&/ {STOP=($0 in T); T[$0]} /^ *$/ {STOP=0} !STOP' file4

awk '/^\*\&/ {STOP=($0 in T)            # if header (identified by *&) is known, stop the printing
              T[$0]                     # remember the header line next time
             } 
     /^ *$/  {STOP=0}                   # empty line: reenable printing
     !STOP                              # use default action: print, if NOT STOPped
    ' file