How to remove all special characters in Linux text

Question

How to remove the special characters shown as blue color in the picture 1 like: ^M, ^A, ^@, ^[. In my understanding, ^M is a windows newline character, I can use sed

Answer 1

To ensure that the command works with limited scope in Sed, force use of the "C" (POSIX) character classifications to avoid unpredictable behavior with non-ASCII characters:

LC_ALL=C sed 's/[^[:blank:][:print:]]//g' file.txt