fgets--not first line

[anonymouse]

When using fgets, how can you get information from the second or third line, etc, instead of just the first line.
what I've got looks like this:

<?php
{
$myFile = "rate.txt";
$fh = fopen($myFile, 'r');
$theData = fgets($fh);
fclose($fh);

echo $theData; 
}
?>

if that's not possible, can you do it with fread and start after a certain character? For instance fread($fh, 5); gives you characters 1-5, but say I only want 6-10.

Any ideas?

[anonymouse]

Well, I figured out a way to go from a desired character to another, as such:

<?php
$fh = fopen("rate.txt", "r");

if(!feof($fh))
{
    fseek($fh, 20);
    echo (fread($fh, 9));
}
fclose($fh);
?>

But then I found a code that claims to be able to go to a specific line, which would be slightly more convenient than counting characters, but I can't really figure out how to get it to work. Here's the code:

<?
   function readLine ($linenum,$fh) {
       $line = fgets ($fh, 4096);
       $pos = -1;
       $i = 0;

       while (!feof($fh) && $i<($linenum-1)) {
           $char = fgetc($fh);
           if ($char != "\n" && $char != "\r") {
               fseek($fh, $pos, SEEK_SET);
               $pos ++;
           }
           else $i ++; 
       }
       $line = fgets($fh);
       return $line;
   } //readLine()
?>

With that...how do I run it and where do I specify the line? I tried just running a readLine(2,"rate.txt"); function and variations of this, but it only produces pages of errors. So, how do I apply this? Thanks!

[anonymouse]

Still no ideas?

[mwinter]

I didn't test the code you posted, but it seemed a little odd to me. By the way, the second argument was supposed to be a file handle, produced by a successful call to fopen, not a file name.

Anyway, this should suit your needs:

function readLine($lineNum, $handle, $length = 1024) {
  $line = false;
  while($lineNum-- && !feof($handle)) {
    $line = fgets($handle, $length);
  }
  return (-1 !== $lineNum) ? false : $line;
} 

It may not necessarily be the most efficient implementation, but that shouldn't matter unless you have a large file. In that instance, I might consider using an index that lists the offset position of each line, or even replacing it all with a database.

The first argument to the function above is desired line, with the first line being 1 (one). The second argument is a file handle, as returned by fopen. The third (optional) argument is the maximum number of characters fgets will read at a time. It defaults to 1024, but if some of your lines are longer, you'll need to pass a more appropriate number.

The fgets function doesn't consider carriage returns (CR; used by Macs) as line separators. However, it handles both line feeds (LF; used by Linux) and CRLF sequences (both; used by Windows) properly. These separators will be included in the returned string so use rtrim to strip them out, if necessary.

If a problem occurs, like trying to read past the end of a file, the function returns false.

Mike

[anonymouse]

Thanks, Mike.

I'm really new to php, so this may seem like a very elementary question. I don't really know how to implement functions...so where do I define each of the arguments? Where do I put the line that establishes the lineNum, handle, etc...I know the handle has to be an fopen, but I can't figure out where to put that. If it's easier, maybe you could just show me an example, say, for instance, if I want line 3 (three) of a file "rate.txt"

The only php I have been able to get to work is just simple lines without functions, so it's simply a lack of understanding of functions. I appreciate your help.

[mwinter]

I don't really know how to implement functions...

Is that implement functions, or use them? There's a bit of a difference.

so where do I define each of the arguments?

That depends on whether you'd want to use them again. You could place the value of each argument in-line with the function call:

myFunction('a string', 32, anotherFunction()); 

assign the values to variables first:

$arg1 = 'a string';
$arg2 = 32;
$arg3 = anotherFunction();

myFunction($arg1, $arg2, $arg3); 

(hopefully using better names), or a mixture of the two as necessary.

Where do I put the line that establishes the lineNum, handle, etc [...]

Well, that's up to you (as I said above)...

If it's easier, maybe you could just show me an example, say, for instance, if I want line 3 (three) of a file "rate.txt"

...but I'll use variables for this example because it's probably clearer.

$desiredLine = 3;
$filename = 'rate.txt';

/* The @ suppresses any error messages that
 * might result from the function call.
 *
 * As we only want to read from the file,
 * it will be opened for reading only.
 */
$fileHandle = @fopen($filename, 'r');

/* However, we can still check if the call
 * succeeded because if it failed,
 * $fileHandle will evaluate to false.
 */
if(!$fileHandle) {
  /* File open operation failed. Do error
   * handling here.
   *
   * Handling mechanisms should be more
   * graceful, but for simplicity, we'll
   * simply stop execution.
   */
  exit();
}

$line = readLine($desiredLine,
                 $fileHandle); 

I hope that helps,
Mike

[anonymouse]

that's pretty much what I was doing before...just figured I must be doing something wrong, so I've been trying a few things, and it's just not working.
Does the function have to be in the <head> section of the script? The experience I have with functions is only through javascript, in writing and using them. So I understand about variables and such.

I keep getting errors like "Parse error: parse error, unexpected T_FUNCTION", which refers to this line:

function readLine($lineNum, $handle, $length = 1024) { 

...this seems to be generating because of the variable $handle, can't figure out why it doesn't like that.

[anonymouse]

Is that implement functions, or use them? There's a bit of a difference.

I guess I mean to call up the function within the script, to echo the line of text.

[Twey]

this seems to be generating because of the variable $handle, can't figure out why it doesn't like that.

I disagree. The parse error means it doesn't expect to find a function definition here. Is there, perhaps, a loop you've forgotten to close?

[nightdriver09]

Does the function have to be in the <head> section of the script? The experience I have with functions is only through javascript, in writing and using them.

php function declaration could be anywhere between the <?php ?> tags.

you could also do this in your readLine function if youre trying to read a not-so-big file.

function readLine( $desiredLine, $handle, $length=1024 )
{
if ( !$handle )
echo 'not a valid handle.';

$ctr = 0;

while ( $ctr!=$desiredLine )
{
$line = fgets( $handle, $length );
if ( feof($handle) )
{
$line = 'error: invalid line number';
break;
}
$ctr++;
}

echo $line;
}