bash check if file does not contains string code example

Example 1: bash if file contains string

if grep -q SomeString "$File"; then
  Some Actions # SomeString was found
fi

Example 2: bash check if string does not exist in file

Just use grep with flags 'F' (fixed string), 'x' (exact match) and 'q'
(quiet output) in order to check if a word string is in a file
if ! grep -Fxq "string" file.txt; then #do some code...#; fi