About Rot13 : https://en.wikipedia.org/wiki/ROT13
Download rot13 by cloning the Git repository:
git clone https://github.com/KasperOmari/Rot13.git
cd Rot13
make main
./main ROTNUMBER FILE {[-d],-e}
** -d to decrypt a file content (default) ** -e to encrypt a file content
This will print decrypted file.txt content in out.txt
./main 13 file.txt > out.txt