replaces blocks of text surrounded by start and end symbol with a constant line (useful for simple preprocessing scripts)

awk.sh

awk '/insert_code_start/,/insert_code_end/  { if ( $0 ~ /insert_code_end/) print "    // insert code here"; next} 1' < test.cpp > text_sub.cpp


# 
# Example 
# 
# void main(){
#   // insert_code_start
#   foo();
#   // insert_code_end
# }
# 
# Turns into 
# void main(){
#   // insert code here
# }