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Top Forums UNIX for Dummies Questions & Answers Want to remove all lines but not latest 50 lines from a file Post 302868905 by drl on Tuesday 29th of October 2013 08:45:28 AM
Old 10-29-2013
Hi.

As alister said.

This behavior has been discussed in the forum, for example, I mentioned sponge / absorb for pipelines and re-writing-in-place in post #8 of https://www.unix.com/shell-programming-and-scripting/221749-run-command-without-over-writing.html -- that approach either keeps data in memory (say a perl array), or writes it to a scratch file first, both of which can preserve the inode if that is important. The sponge approach looks like the tee solution, but the internal logic differs by sponge collecting all the data until the end, then writing to the file argument, whereas tee streams the data to the file(s) as it comes in.

We cannot use the scratch file approach here because there is no additional disk space, so suggestions like the shell and dd above seemed appropriate. Both were validated on a file of 14M lines (~ 1 GB) with 50,000 lines being kept.

Best wishes ... cheers, drl

Last edited by drl; 10-30-2013 at 11:53 AM.. Reason: Minor typo.
 

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OUTPUT_ADD_REWRITE_VAR(3)						 1						 OUTPUT_ADD_REWRITE_VAR(3)

output_add_rewrite_var - Add URL rewriter values

SYNOPSIS
bool output_add_rewrite_var (string $name, string $value) DESCRIPTION
This function adds another name/value pair to the URL rewrite mechanism. The name and value will be added to URLs (as GET parameter) and forms (as hidden input fields) the same way as the session ID when transparent URL rewriting is enabled with session.use_trans_sid. Please note that absolute URLs (http://example.com/..) aren't rewritten. This function's behavior is controlled by the url_rewriter.tags php.ini parameter. Note Calling this function will implicitly start output buffering if it is not active already. PARAMETERS
o $name - The variable name. o $value - The variable value. RETURN VALUES
Returns TRUE on success or FALSE on failure. EXAMPLES
Example #1 output_add_rewrite_var(3) example <?php output_add_rewrite_var('var', 'value'); // some links echo '<a href="file.php">link</a> <a href="http://example.com">link2</a>'; // a form echo '<form action="script.php" method="post"> <input type="text" name="var2" /> </form>'; print_r(ob_list_handlers()); ?> The above example will output: <a href="file.php?var=value">link</a> <a href="http://example.com">link2</a> <form action="script.php" method="post"> <input type="hidden" name="var" value="value" /> <input type="text" name="var2" /> </form> Array ( [0] => URL-Rewriter ) SEE ALSO
output_reset_rewrite_vars(3), ob_flush(3), ob_list_handlers(3). PHP Documentation Group OUTPUT_ADD_REWRITE_VAR(3)
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