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Full Discussion: Split a file with no pattern -- Split, Csplit, Awk
Top Forums UNIX for Dummies Questions & Answers Split a file with no pattern -- Split, Csplit, Awk Post 302151805 by drl on Monday 17th of December 2007 11:57:24 AM
Old 12-17-2007
Hi.
Quote:
Originally Posted by radoulov
...
If you want the number of files/parts,
it's important if the total number of lines in the bigfile is known a priori
(otherwise it will be slower, because we have to read it twice: first to get
the number of lines, and then again to split it).
This does not appear to need absolute precision. You can read the first 100 (or few hundreds) of lines, then seek to near the end, read another 100 or so until the end, then calculate the mean length of the lines you saw. Obtaining the length of the file is cheap -- Linux has a stat command, but one could cut the length out from "ls -l". Divide the length in bytes by the estimated mean length and you get an estimate of the number of lines.

If necessary, one could also read a section from the middle (or elsewhere) to increase the accuracy.

The key is using a seek for positioning, and stat for the length -- both are very fast ... cheers, drl
 

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LEARN ABOUT SUNOS

lptest

lptest(1B)					     SunOS/BSD Compatibility Package Commands						lptest(1B)

NAME

       lptest - generate line printer ripple pattern

SYNOPSIS

       /usr/ucb/lptest [ length [count]]

DESCRIPTION

       The  lptest  utility  writes the traditional ripple test pattern to the standard output. In 96 lines, the ripple test pattern prints all 96
       printable ASCII characters in each position. The ripple test pattern was originally created to test printers.  It is also useful for  test-
       ing terminals, driving terminal ports, debugging, and performing tasks that require a quick supply of random data.

       This command is obsolete.

OPTIONS

       length	       Specifies the length of the output line in characters. 79 characters is the default.

       count	       Specifies the number of output lines. 200 lines is the default. If  count is specified, length must also be specified.

EXIT STATUS

       The following exit values are returned:

       0	       Successful completion.

       non-zero        An error occurred.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWscplp 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       attributes(5)

SunOS 5.10							    9 Sep 1996								lptest(1B)
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