od.1posix -vAn -N4 -tu4 < /dev/urandom
dump files in various formats
-v     Write all input data. Without the -v option, any number of groups of output lines, which would  be
       identical  to the immediately preceding group of output lines (except for the byte offsets), shall
       be replaced with a line containing only an asterisk ( '*' ).
-N  count
       Format  no  more  than  count  bytes of input. By default, count shall be interpreted as a decimal
       number. With a leading 0x or 0X, count shall be interpreted as a  hexadecimal  number;  otherwise,
       with  a  leading  '0' , it shall be interpreted as an octal number. If count bytes of input (after
       successfully skipping, if -j skip is specified) are not available, it shall not be  considered  an
       error; the od utility shall format the input that is available.
Before a command is executed, its input and output may be redirected using a special notation interpreted
by  the  shell.   Redirection  may  also  be used to open and close files for the current shell execution
environment.  The following redirection operators may precede or appear anywhere within a simple  command
or may follow a command.  Redirections are processed in the order they appear, from left to right.

Redirecting Input
    Redirection  of  input  causes  the  file  whose name results from the expansion of word to be opened for
    reading on file descriptor n, or the standard input (file descriptor 0) if n is not specified.

    The general format for redirecting input is:

source manpages: od