Find specific pattern and print complete text block using awk or sed

Question

How can find a specific number in a text block and print the complete text block beginning with the key word \"BEGIN\" and ending with \"

Answer 1

$ awk -v RS= -v ORS='\n\n' '/\nB: 567/' file
BEGIN
A: xyz
B: 56789
C: abc
END

BEGIN
A: ghi
B: 56712
C: pqr
END

Note the \n before B to ensure it occurs at the start of a line.This is in place of the ^ start-of-string character you had originally since now each line isn't it's own string. You need to set ORS above to re-insert the blank line between records.