Thursday Quote: Dan Wineman
You say “looks like somebody has too much time on their hands” but all I hear is “I’m sad because I don’t know what creativity feels like.”
Thursday Quote: William Gibson
“My problem is that all things are increasingly interesting to me.”
– William Gibson
During A Talk On “Zero History”
Tail In PHP
So I’m working on a little admin interface and I decided to tail some logs. It’s in PHP and Google came up with some stuff, but they were all a bit finickey and not well documented. So I wrote my own!
Here’s the basic concept:
- Open File
- Seek To End
- Loop:
- Seek Back By Chunk Size
- Read Chunk
- Count Newlines
- Stash In Buffer
- Break If Enough Newlines Total
- Trim Extra Line & Cruft
- Done!
Here’s the code:
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function tail ( $file, $lines, $max_chunk_size = 4096 ) { // We actually want to look for +1 newline so we can get the whole first line $rows = $lines + 1; // Open up the file $fh = fopen( $file, 'r' ); // Go to the end fseek( $fh, 0, SEEK_END ); $position = ftell( $fh ); $buffer = ''; $found_newlines = 0; $break = false; while( ! $break ) { // If we are at the start then we are done. if( $position <= 0 ) { break; } // We can't seek past the 0 position obviously, so figure out a good chunk size $chunk_size = ( $max_chunk_size > $position ) ? $position : $max_chunk_size; // Okay, now seek there and read the chunk $position -= $chunk_size; fseek( $fh, $position ); $chunk = fread( $fh, $chunk_size ); // See if there are any newlines in this chunk, count them if there are if( false != strpos( $chunk, "\n" ) ) { if( substr( $chunk, -1 ) == "\n" ) { ++$found_newlines; } $found_newlines += count( explode( "\n", $chunk ) ); } // Have we exceeded our desired rows? if( $found_newlines > $rows ) { $break = true; } // Prepend $buffer = $chunk . $buffer; } // Now extract only the lines we requested $buffer = explode( "\n", $buffer ); return implode( "\n", array_slice( $buffer, count( $buffer ) - $lines ) ); } |
You can give it a try on some junk data here: http://static.velvetcache.org/pages/2010/12/03/tail-in-php/
Thursday Quote: C. Scott Andreas
“If you are afraid of your program, troche you have to break it until you are not afraid of it anymore.”
– C. Scott Andreas
You Have to Break It
Headless VirtualBox
Updated (2010-12-02)
So, duh, multiple interfaces. One NAT one Host-Only. All done.
I recently set up a VirtualBox VM to test BlankSMTP locally, but it’s annoying to have the GUI up all the time when I’m just SSH’ing in. To get around this I set it up to work headless.
The biggest hangup is networking. I had to switch it to Host-Only so that the interface would remain consistent. Other wise with bridged I would get new IP’s all the time, and even then only when the networking init script got triggered somehow.
After that was set I just wrote two quick bash scripts to start and stop. An init script would also be an option if I wanted to make sure it shut down when I power off the laptop, but I decided it wasn’t worth the trouble.
The key commands are VBoxHeadless -startvm [vm name] and VBoxManage controlvm [vm name] savestate
blanksmtp-start
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#!/bin/bash COUNT=$( ps aux | grep 'VBoxHeadless -startvm BlankSMTP' | grep -v grep | wc -l) if [ "$COUNT" == "0" ]; then echo "Starting BlankSMTP..." nohup VBoxHeadless -startvm BlankSMTP > /dev/null 2>&- & else echo "Found a running instance!" fi |
blanksmtp-stop
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#!/bin/bash COUNT=$( ps aux | grep 'VBoxHeadless -startvm BlankSMTP' | grep -v grep | wc -l) if [ "$COUNT" == "0" ]; then echo "No running instance!" else echo "Shutting down..." VBoxManage controlvm BlankSMTP savestate fi |
Works like a charm!