Escaping regex-active characters

Question

var="int foo(float y, bool k)"
awk -v start="$var" '
$0 ~ start ,$0 ~ /}/{
print
if($0 ~ start ){ startLine=FNR }
if($0~/}/){ 
   print "The content is between lines " startLine " and " FNR
   exit
}
}' $file

I want to search for a string in a file, but because the string contains parentheses it recognizes them as a operator rather than a character. I tried this

var="int foo\(float y, bool k\)"

and it does solve the issue, but my var isn't always the same so in that case I would neeed some code that adds a backslash before parentheses. Is there any other solution?

Answer 1

Based on your shown samples, could you please try following. Quote your shell variable inside '...'(single quotes) to make characters inside literal character. Also I have changed approach here and used index rather than using range method of awk this is more suitable on this kind of situations.

start='int foo(float y, bool k)'
awk -v start="$start" '
index($0,start){
  found=1
  startLine=FNR
}
found{
  val=(val?val ORS:"")$0
}
$0 ~ /}/{
  if(val){  print val }
   print "The content is between lines " startLine " and " FNR
   exit
}'  Input_file

Answer 2

Use index instead.

index($0, start)