Validates a command line argument.
Validates a command line argument.
Validates that the argument does not refer to anything on the filesystem.
Validates that argument refers to a valid directory.
Validates that argument refers to a valid file.
Makes sure a given argument is a negative number (n <= 0).
Validates that the string is not empty.
Checks that a given argument is a valid port number (n > 0 && n < 65536).
Makes sure a given argument is a positive number (n >= 0).