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Top Forums Shell Programming and Scripting A script that processes a sample of a file Post 302818577 by Don Cragun on Friday 7th of June 2013 08:54:53 PM
Old 06-07-2013
Quote:
Originally Posted by Jotne
Code:
awk 'BEGIN {srand()} !/^$/ { if (rand() <= .01) print $0}' file

Should give you ca 10% of the file
According to the standards, awk's rand() function returns a pseudo-random number x such that 0 < x < 1. If we assume that the pseudo-random number is uniformly distributed (which is not required by the standards), then (rand() <= .01) should be true approximately 1% of the time. For 10%, the test would be ICODE](rand() <= .1)[/ICODE] (again, assuming rand() produces a uniformly distributed set of values).

Note that when using "random" numbers, there is certainly no guarantee that using (rand() <= 10000/200000) as the test in Jotne's script will print exactly 10,000 lines from a 200,000 line file.
 

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RDSWAP(1)						      General Commands Manual							 RDSWAP(1)

["NAME"]
       rdswap - a multi-language RD documents support tool

["SYNOPSIS"]
       rdswap [ -h | -v ] filename ...

["DESCRIPTION"]
       This tool is written to support you to write multi-language documents using the Ruby-Document-Format (RD).

       The idea for such a tool was originated by Minero Aoki, how has thought about, how to make life easier for developers who have to write and
       maintain scripts in more than one language.

       You have to specify at least two filenames on the command line. One containing the Ruby script, the second containing a translated  RD.	If
       the  script  does  not  end  with `.rb', it has to be the first filename mentioned on the command line! In opposition, all files containing
       translations must not ending with `.rb'! They should use a extension that describes the language. So that would give us the following  pic-
       ture:

	      o sample.rb : Script contains the original documentation.

	      o sample.jp : Documentation written in Japanese.

	      o sample.de : Translation to German.

       The  tool doesn't care about the language extensions. You can name them as you like! So the file containing the Japanese translation above,
       could also be names e.g. `sample.japan' or even `japantranslation.japan'.

       For every translation file, a new file will be created. The name is build from the script filename plus the language extension. So  regard-
       ing the example above, following files would be created:

	      o sample.rb.jp

	      o sample.rb.de

       or, given the alternative translation filename as mentioned above...

	      o sample.rb.japan

   ["How does it work?"]
       The  contents  of all files will be split into source and RD blocks. The source of the translation files, will be discarded! Every RD block
       may be of a certain type. The type will be taken from the contents directly following the `=begin' on the same line. If	there  is  only  a
       lonely `=begin' on a line by itself, the type of the block is `nil'. That means in
	   # File sample.rd
	   :
	   =begin
	    bla bla
	   =end
	   :
	   =begin whatever or not
	    blub blub
	   =end
	   :

       the first block would be of type `nil' and the second one of type `whatever or not'.

       Block  types  are  important for the translation. If a source will be generated from a script and a translation file, only these blocks are
       taken from the translation files, that comes in the right sequence and contains the same type as the block in the script! For example:
	   # File sample.rb
	   :
	   =begin gnark
	    Some comment
	   =end
	   :
	   =begin
	    block 2
	   =end
	   :
	   =begin
	    block 3
	   =end
	   :

	   # File sample.de
	   :
	   =begin
	    Block zwei
	   =end
	   :
	   =begin
	    Block drei
	   =end
	   :

       Here, the first block of `sample.rb' will *not* be translated, as there is no translation block with that type in sample.de! So	the  first
       block  would  be  inserted as-it-is into the translated script. The blocks afterwards, however, are translated as the block type does match
       (it is `nil' there).

       Attention: In a translation file, a second block will only be used, if a first one was already used (matched). A third block will  only	be
       used, if a second one was used already!

       That  means,  if the first block of `sample.de' would be of type e.g. `Never match', then no block would ever be taken to replace anyone of
       `sample.rb'.

   ["OPTIONS"]
       ["-h"]
	      shows this help text.

       ["-v"]
	      shows some more text during processing.

       ["filename"]
	      means a file, that contains RD and/or Ruby code.

   ["EXAMPLES"]
	   rdswap -v sample.rb sample.ja sample.de
	   rdswap -v sample.ja sample.rb sample.de
	   rdswap -v sample.ja sample.de sample.rb
	   rdswap -v sample.??

   ["AUTHORS"]
       Clemens Hintze <c.hintze@gmx.net>.

								     June 2012								 RDSWAP(1)
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