grep: input file 'X' is also the output

It is not possible to use the same file as input and output for grep. You may consider the following alternatives:

• temporary file

  grep pattern file > tmp_file
  mv tmp_file file
  

• sed

  sed -i -n '/pattern/p' file
  

• put whole file in the variable (not bright idea for large files)

  x=$(cat file); echo "$x" | grep pattern > file
  

You can use the --exclude field in your grep command like so:

grep  --exclude=myfile  -Eron  r"%}(.*){%"  >  myfile