PHP to delete lines within text file beginning with 0 or a negative number

Question

Hi there,

Thank you for taking the time to read this and I will appreciate every single response no mater the quality of content. :)

Using php, I'm trying to create a script which will delete several lines within a text file (.txt) if required, based upon whether the line starts with a 0 or a negative number. Each line within the file will always start with a number, and I need to erase all the neutral and/or negative numbers.

The main part I'm struggling with is that the content within the text file isn't static (e.g. contain x number of lines/words etc.) Infact, it is automatically updated every 5 minutes with several lines. Therefore, I'd like all the lines containing a neutral or negative number to be removed.

The text file follows the structure:

-29 aullah1
0 name
4 username
4 user
6 player

If possible, I'd like Line 1 and 2 removed, since it begins with a neutral/negative number. At points, there maybe times when there are more than two neutral/negative numbers.

All assistance is appreciated and I look forward to your replies; thank you. :) If I didn't explain anything clearly and/or you'd like me to explain in more detail, please reply. :)

Thank you.

Answer 1

Example:

$file = file("mytextfile.txt");
$newLines = array();
foreach ($file as $line)
    if (preg_match("/^(-\d+|0)/", $line) === 0)
        $newLines[] = chop($line);
$newFile = implode("\n", $newLines);
file_put_contents("mytextfile.txt", $newFile);

It is important that you chop() the newline character off of the end of the line so you don't end up with empty space. Tested successfully.

Answer 2

Load whole line into variable trim it and then check if first letter is - or 0.

$newContent = "";
$lines = explode("\n" , $content);
foreach($lines as $line){
  $fChar = $line[0];
  if(!($fChar == '0' || $fChar == '-'))
  $newContent .= $line."\n";
}

I changed malik's code for better performance and quality.

Answer 3

Something on these lines i guess, it is untested.

$newContent = "";
$lines = explode("\n" , $content);
foreach($lines as $line){
  $fChar = substr($line , 0 , 1);
  if($fChar == "0" || $fChar == "-") continue;
  else $newContent .= $line."\n";
}

Answer 4

If the file is big, its better to read it line by line as:

$fh_r = fopen("input.txt", "r");  // open file to read.
$fh_w = fopen("output.txt", "w"); // open file to write.

while (!feof($fh_r)) { // loop till lines are left in the input file.
        $buffer = fgets($fh_r); //  read input file line by line.

        // if line begins with num other than 0 or -ve num write it. 
        if(!preg_match('/^(0|-\d+)\b/',$buffer)) { 
                fwrite($fh_w,$buffer);
        }       
}       

fclose($fh_r);
fclose($fh_w);

Note: Err checking not included.

Answer 5

file_put_contents($newfile, 
    implode(
        preg_grep('~^[1-9]~', 
            file($oldfile))));

php is not particularly elegant, but still...

Answer 6

Here's another way:

class FileCleaner extends FilterIterator
{
    public function __construct($srcFile)
    {
        parent::__construct(new ArrayIterator(file($srcFile)));
    }

    public function accept()
    {
        list($num) = explode(' ', parent::current(), 2);
        return ($num > 0);
    }

    public function write($file)
    {
        file_put_contents($file, implode('', iterator_to_array($this)));
    }
}

Usage:

$filtered = new FileCleaner($src_file);
$filtered->write($new_file);

Logic and methods can be added to the class for other stuff, such as sorting, finding the highest number, converting to a sane storage method such as csv, etc. And, of course, error checking.