Insert a prefix into the data to be digested. By using -p prefix , one may prepend any set of data with a string. The digest produced is equivalent to digest that is produced with the string pretended to the data. By use of the -P prefile interface, one may prepend using up to the 32k of a file. This interface allows one to prepend using binary data.
Output only digests.
The filename or string will not be written to stdout. The trailing NUL byte is not digested. No files are digested. The str is written to stdout enclosed in double quotes. Time the user cpu seconds needed to digest several megabytes of data.