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dd - binary file

 
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Old 12-04-2008
dd - binary file
I have a task that says: make a file (called binaryfile ) that contains
4 bytes of NULL data
6 bytes of random data
8 bytes of 1
10 bytes of 5
and 12 bytes of 9.

For the first 2, I can used :
dd if=/dev/null of=binaryfile bs=8 count =4 and
dd if=/dev/urandom of=binaryfile bs=8 count=6 seek=4, but how can I do the rest ???
I know, bs will remain 8 (8 bits) and seek will increase after each append to my file. My question is, how to tell dd what bits to copy (other than 0 or random).
 
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LEARN ABOUT MOJAVE

bytes5.18

bytes(3pm)						 Perl Programmers Reference Guide						bytes(3pm)

NAME

       bytes - Perl pragma to force byte semantics rather than character semantics

NOTICE

       This pragma reflects early attempts to incorporate Unicode into perl and has since been superseded. It breaks encapsulation (i.e. it
       exposes the innards of how the perl executable currently happens to store a string), and use of this module for anything other than
       debugging purposes is strongly discouraged. If you feel that the functions here within might be useful for your application, this possibly
       indicates a mismatch between your mental model of Perl Unicode and the current reality. In that case, you may wish to read some of the perl
       Unicode documentation: perluniintro, perlunitut, perlunifaq and perlunicode.

SYNOPSIS

	   use bytes;
	   ... chr(...);       # or bytes::chr
	   ... index(...);     # or bytes::index
	   ... length(...);    # or bytes::length
	   ... ord(...);       # or bytes::ord
	   ... rindex(...);    # or bytes::rindex
	   ... substr(...);    # or bytes::substr
	   no bytes;

DESCRIPTION

       The "use bytes" pragma disables character semantics for the rest of the lexical scope in which it appears.  "no bytes" can be used to
       reverse the effect of "use bytes" within the current lexical scope.

       Perl normally assumes character semantics in the presence of character data (i.e. data that has come from a source that has been marked as
       being of a particular character encoding). When "use bytes" is in effect, the encoding is temporarily ignored, and each string is treated
       as a series of bytes.

       As an example, when Perl sees "$x = chr(400)", it encodes the character in UTF-8 and stores it in $x. Then it is marked as character data,
       so, for instance, "length $x" returns 1. However, in the scope of the "bytes" pragma, $x is treated as a series of bytes - the bytes that
       make up the UTF8 encoding - and "length $x" returns 2:

	   $x = chr(400);
	   print "Length is ", length $x, "
";     # "Length is 1"
	   printf "Contents are %vd
", $x;	    # "Contents are 400"
	   {
	       use bytes; # or "require bytes; bytes::length()"
	       print "Length is ", length $x, "
"; # "Length is 2"
	       printf "Contents are %vd
", $x;     # "Contents are 198.144"
	   }

       chr(), ord(), substr(), index() and rindex() behave similarly.

       For more on the implications and differences between character semantics and byte semantics, see perluniintro and perlunicode.

LIMITATIONS

       bytes::substr() does not work as an lvalue().

SEE ALSO

       perluniintro, perlunicode, utf8

perl v5.18.2							    2013-11-04								bytes(3pm)