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fgets

(PHP 4, PHP 5)

fgets — Obtiene una línea desde el puntero a un fichero

Descripción

string fgets ( resource $handle [, int $length ] )

Obtiene una línea desde el puntero al fichero.

Parámetros

handle: El fichero al que se apunta debe ser válido, y debe apuntar a un fichero abierto por fopen() o fsockopen() (y que todavía no esté cerrado por fclose()).
length: La lectura termina cuando se han leído length - 1 bytes, o una nueva línea (la cual está incluida en el valor de retorno), o un EOF (lo que suceda primero). Si no se especifica una longitud, se serguirá leyendo desde el flujo hasta que alcance el final de la línea.

Nota:
Hasta PHP 4.3.0, al omitirlo se asumía una longitud de línea de 1024. Si la mayoría de las lineas del fichero son todas mayores de 8KB, es más eficiente para el script en cuestión de recursos especificar la longitud máxima de línea.

Valores devueltos

Devuelve una cadena de hasta length - 1 bytes leídos desde el fichero apuntado por handle. Si no hay más datos que leer en el puntero al fichero, devuelve FALSE.

Si se produjo un error, devuelve FALSE.

Historial de cambios

Versión	Descripción
4.3.0	fgets() ahora es segura al trabajar con datos binarios
4.2.0	El parámetro `length` se volvió opcional

Ejemplos

Ejemplo #1 Leer un fichero línea a línea


<?php
$gestor = @fopen("/tmp/inputfile.txt", "r");
if ($gestor) {
    while (($búfer = fgets($gestor, 4096)) !== false) {
        echo $búfer;
    }
    if (!feof($gestor)) {
        echo "Error: fallo inesperado de fgets()\n";
    }
    fclose($gestor);
}
?>

Notas

Nota: Si sufre problemas con PHP no reconociendo los finales de línea cuando lee o crea ficheros en Macintosh, puede probar de activar la opción de configuración en tiempo de ejecución auto_detect_line_endings para intentar resolver el problema.

Nota:
Las personas que suele usar la semántica tipo 'C' de fgets() deberían observar la diferencia de cómo se devuelve EOF.

Ver también

fgetss() - Obtiene un línea desde un puntero a un archivo y elimina las etiquetas HTML
fread() - Lectura de un fichero en modo binario seguro
fgetc() - Obtiene un carácter de un puntero a un archivo
stream_get_line() - Obtiene una línea del recurso de flujo hasta un delimitador dado
fopen() - Abre un fichero o una URL
popen() - Abre un proceso de un puntero a un fichero
fsockopen() - Abre una conexión vía sockets a Internet o a un dominio Unix
stream_set_timeout() - Establecer un perido de tiempo de espera en un flujo

add a note

User Contributed Notes 29 notes

down

Dade Brandon ¶

10 months ago


Regarding Leigh Purdie's comment (from 4 years ago) about stream_get_line being better for large files, I decided to test this in case it was optimized since then and I found out that Leigh's comment is just completely incorrect

fgets actually has a small amount of better performance, but the test Leigh did was not set up to produce good results

The suggested test was:

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,65535,"\n")) { 1; } fclose($fp);'

0m1.616s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,65535)) { 1; } fclose($fp);'

0m7.392s

The reason this is invalid is because the buffer size of 65535 is completely unnecessary

piping the output of "yes 'this is a test line'" in to PHP makes each line 19 characters plus the delimiter

so while I don't know why stream_get_line performs better with an oversize buffer, if both buffer sizes are correct, or default, they have a negligable performance difference - although notably, stream_get_line is consistent - however if you're thinking of switching, make sure to be aware of the difference between the two functions, that stream_get_line does NOT append the delimiter, and fgets DOES append the delimiter

Here are the results on one of my servers:

Buffer size 65535
stream_get_line:    0.340s
fgets:   2.392s

Buffer size of 1024
stream_get_line:  0m0.348s
fgets: 0.404s

Buffer size of 8192 (the default for both)
stream_get_line: 0.348s
fgets:  0.552s

Buffer size of 100:
stream_get_line: 0.332s
fgets: 0.368s

down

afwxkat at gmail dot com ¶

5 years ago


One thing I discovered with fgets, at least with PHP 5.1.6, is that you may have to use an IF statement to avoid your code running rampant (and possibly hanging the server).  This can cause problems if you do not have root access on the server on which you are working.



This is the code I have implemented ($F1 is an array):



<?php

   if($fh = fopen("filename","r")){

      while (!feof($fh)){

         $F1[] = fgets($fh,9999);

      }

      fclose($fh);

    }

?>



I have noticed that without the IF statement, fgets seems to ignore when $fh is undefined (i.e., "filename" does not exist).  If that happens, it will keep attempting to read from a nonexistent filehandle until the process can be administratively killed or the server hangs, whichever comes first.

down

Peter Schlaile ¶

6 years ago


fscanf($file, "%s\n") isn't really a good substitution for fgets(), since it will stop parsing at the first whitespace and not at the end of line!

(See the fscanf page for details on this)

down

kpeters AT-AT monolithss DEE OH TEE com ¶

8 years ago


It appears that fgets() will return FALSE on EOF (before feof has a chance to read it), so this code will throw an exception:

while (!feof($fh)) {
  $line = fgets($fh);
  if ($line === false) {
    throw new Exception("File read error");
  }
}

down

sam dot bryan at montal dot com ¶

8 years ago


An easy way to authenticate Windows Domain users from scripts running on a non-Windows or non-Domain box - pass the submitted username and password to an IMAP service on a Windows machine.

<?php
$server = 'imapserver';
$user = 'user';
$pass = 'pass';

if (authIMAP($user, $pass, $server)) {
    echo "yay";
} else {
    echo "nay";
}

function authIMAP($user, $pass, $server) {
    $connection = fsockopen($server, 143, $errno, $errstr, 30);

    if(!$connection) return false;

    $output = fgets($connection, 128); // banner
    fputs($connection, "1 login $user $pass\r\n");
    $output = fgets($connection, 128);
    fputs($connection, "2 logout\r\n");
    fclose($connection);

    if (substr($output, 0, 4) == '1 OK') return true;

    return false;
}
?>

down

hackajar <matt> yahoo <trot> com ¶

8 years ago


When working with VERY large files, php tends to fall over sideways and die.  

Here is a neat way to pull chunks out of a file very fast and won't stop in mid line, but rater at end of last known line.  It pulled a 30+ million line 900meg file through in ~ 24 seconds.

NOTE: 
$buf just hold current chunk of data to work with.  If you try "$buf .=" (note 'dot' in from of '=') to append $buff, script will come to grinding crawl around 100megs of data, so work with current data then move on!

//File to be opened
$file = "huge.file";
//Open file (DON'T USE a+ pointer will be wrong!)
$fp = fopen($file, 'r');
//Read 16meg chunks
$read = 16777216;
//\n Marker
$part = 0;

while(!feof($fp)) {
    $rbuf = fread($fp, $read);
    for($i=$read;$i > 0 || $n == chr(10);$i--) {
        $n=substr($rbuf, $i, 1);
        if($n == chr(10))break;
        //If we are at the end of the file, just grab the rest and stop loop
        elseif(feof($fp)) {
            $i = $read;
            $buf = substr($rbuf, 0, $i+1);
            break;
        }
    }
    //This is the buffer we want to do stuff with, maybe thow to a function?
    $buf = substr($rbuf, 0, $i+1);
    //Point marker back to last \n point
    $part = ftell($fp)-($read-($i+1));
    fseek($fp, $part);
}
fclose($fp);

down

lzsiga at freemail.c3.hu ¶

4 years ago


Some people try to call feof before fgets, and then ignoring the return value of fgets. This method leads to processing value FALSE when reaching the end of file.

Bad example:
<?php
    $f = fopen ("fgetstest.php", "r");
    $ln= 0;
    while (! feof ($f)) {
        $line= fgets ($f);
        ++$ln;
        printf ("%2d: ", $ln);
        if ($line===FALSE) print ("FALSE\n");
        else print ($line);
    }
    fclose ($f);
?>

Good example:
<?php
    $f = fopen ("fgetstest.php", "r");
    $ln= 0;
    while ($line= fgets ($f)) {
        ++$ln;
        printf ("%2d: ", $ln);
        if ($line===FALSE) print ("FALSE\n");
        else print ($line);
    }
    fclose ($f);
?>

down

Leigh Purdie ¶

5 years ago


For large files, consider using stream_get_line rather than fgets - it can make a significant difference.

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,65535,"\n")) { 1; } fclose($fp);'

real    0m1.482s
user    0m1.616s
sys    0m0.152s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,65535)) { 1; } fclose($fp);'

real    0m7.281s
user    0m7.392s
sys    0m0.136s

down

wojons ¶

5 months ago


This goes out to Leigh Purdie (5 years ago) and also Dade Brandon (4 months ago)

So i say Leigh posting and though omg i need to change all my fgets to stream_get_line. Then i ran the tests as shown in Leigh Purdie comment His results:

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,65535,"\n")) { 1; } fclose($fp);'

real    0m1.482s
user    0m1.616s
sys    0m0.152s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,65535)) { 1; } fclose($fp);'

real    0m7.281s
user    0m7.392s
sys    0m0.136s

My Results:

$  time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,65535,"\n")) { 1; } fclose($fp);'

real    0m0.341s
user    0m0.352s
sys    0m0.148s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,65535)) { 1; } fclose($fp);'

real    0m4.283s
user    0m4.128s
sys    0m0.448s

My results do show the same issue his results show. But first off PHP has at least gotten about 2-5 times faster then when the tests were first run (or better hardware).

Now to relate to Dade Brandon who states if you use a correct buffer size the perfomance is neck and neck. 

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,21,"\n")) { 1; } fclose($fp);'

real    0m0.336s
user    0m0.412s
sys    0m0.076s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,21)) { 1; } fclose($fp);'

real    0m0.312s
user    0m0.364s
sys    0m0.192s

As you can see very close and fgets just coming just a little bit ahead. I suspect that fgets is reading backwards on the buffer or loads everything into its self then trys to figure it out where as a correct set buffer does the trick. Dade Brandon states that fgets lets you know how the line was delimited. stream_get_line lets you choose what you wanna call the delimiter using its 3rd option.

fgets has one more option that is important, you dont have to set the length of the line. So in a case where you may not know the length of the line maybe in handling Http protocol or something else like log lines you can simply leave it off and still get great performance.

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp)) { 1; } fclose($fp);'

real    0m0.261s
user    0m0.260s
sys    0m0.232s

This is better then with a buffer set.

down

Anonymous ¶

5 months ago


This goes out to Leigh Purdie (5 years ago) and also Dade Brandon (4 months ago)

So i say Leigh posting and though omg i need to change all my fgets to stream_get_line. Then i ran the tests as shown in Leigh Purdie comment His results:

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,65535,"\n")) { 1; } fclose($fp);'

real    0m1.482s
user    0m1.616s
sys    0m0.152s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,65535)) { 1; } fclose($fp);'

real    0m7.281s
user    0m7.392s
sys    0m0.136s

My Results:

$  time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,65535,"\n")) { 1; } fclose($fp);'

real    0m0.341s
user    0m0.352s
sys    0m0.148s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,65535)) { 1; } fclose($fp);'

real    0m4.283s
user    0m4.128s
sys    0m0.448s

My results do show the same issue his results show. But first off PHP has at least gotten about 2-5 times faster then when the tests were first run (or better hardware).

Now to relate to Dade Brandon who states if you use a correct buffer size the perfomance is neck and neck. 

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=stream_get_line($fp,21,"\n")) { 1; } fclose($fp);'

real    0m0.336s
user    0m0.412s
sys    0m0.076s

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp,21)) { 1; } fclose($fp);'

real    0m0.312s
user    0m0.364s
sys    0m0.192s

As you can see very close and fgets just coming just a little bit ahead. I suspect that fgets is reading backwards on the buffer or loads everything into its self then trys to figure it out where as a correct set buffer does the trick. Dade Brandon states that fgets lets you know how the line was delimited. stream_get_line lets you choose what you wanna call the delimiter using its 3rd option.

fgets has one more option that is important, you dont have to set the length of the line. So in a case where you may not know the length of the line maybe in handling Http protocol or something else like log lines you can simply leave it off and still get great performance.

$ time yes "This is a test line" | head -1000000 | php -r '$fp=fopen("php://stdin","r"); while($line=fgets($fp)) { 1; } fclose($fp);'

real    0m0.261s
user    0m0.260s
sys    0m0.232s

This is better then with a buffer set.

down

hgs at cs dot columbia dot edu ¶

3 years ago


There seems to be an interaction between sockets and the auto_detect_line_endings setting that can cause rather peculiar behavior. Apparently, if the first line read from a socket is split across two TCP packets, the detector will look at the first TCP packet and determine that the system uses MacOS (\r) line endings, even though the LF is contained in the next packet. For example, this affected the PEAR Net_SMTP package, which would fail mysteriously for only some email servers.

down

jerem-NoSpam-ified at live dot com ¶

6 years ago


It's worth noting that this function only assumes chr(10) as a line break, but not chr(13). Personally, I prefer using chr(13) as a line break.

down

Daniel Klein ¶

6 years ago


The file pointer that fgets() uses can also be created with the proc_open() function and used with the stdout pipe created from the executed process.

down

david_sitller at blackbit dot de ¶

6 years ago


If you use the example from the command-description, i recommend to trim the $buffer for further use. The line feed ist still at the end of the line. I saw this when using PHP CLI.

Like this, checking a file-list for existing entries:

$handle = fopen ("/tmp/files.txt", "r");
while (!feof($handle)) {
    $buffer = fgets($handle, 4096);
    if (file_exists(rtrim($filename,"\n"))) {
        echo $buffer;
    } else {
        echo $buffer." has been removed."
}
fclose ($handle);

down

anacreo has gmail ¶

6 years ago


I'm using this function to modify the header of a large postscript document on copy...  Works extremely quickly so far...

function write($filename) {
     $fh = fopen($this->sourceps,'r');
     $fw = fopen($filename,'w');

     while (!feof($fh)) {
       $buffer = fgets($fh);
       fwrite($fw,$buffer);
       if (!$setupfound && ereg("^%%BeginSetup",$buffer)) {
         $setupfound++;
         if (array_key_exists("$filename",$this->output)) {
           foreach ($this->output[$filename] as $function => $value) {
             fwrite($fw,$value);
           }
         }
         stream_copy_to_stream($fh,$fw);
       }
     }
     fclose($fw);
     fclose($fh);
   }

down

David at Weintraub.name ¶

7 years ago


There's an error in the documentation:

The file pointer must be valid, and must point to a file successfully opened by fopen() or fsockopen() (and not yet closed by fclose()).

You should also add "popen" and "pclose" to the documentation. I'm a new PHP developer and went to verify that I could use "fgets" on commands that I used with "popen".

down

d at foo.com ¶

7 years ago


For sockets, If you dont want fgets, fgetc etc... to block if theres no data there. set socket_set_blocking(handle,false); and socket_set_blocking(handle,true); to set it back again.

down

svayn at yahoo dot com ¶

8 years ago


fgets is SLOW for scanning through large files. If you don't have PHP 5, use fscanf($file, "%s\n") instead.

down

Anonymous ¶

8 years ago


Macintosh line endings mentioned in docs refer to Mac OS Classic. You don't need this setting for interoperability with unixish OS X.

down

tavernadelleidee[italy] ¶

8 years ago


I think that the quickest way of read a (long) file with the rows in  reverse order is

<?php
$myfile = 'myfile.txt';
$command = "tac $myfile > /tmp/myfilereversed.txt";
passthru($command);
$ic = 0;
$ic_max = 100;  // stops after this number of rows
$handle = fopen("/tmp/myfilereversed.txt", "r");
while (!feof($handle) && ++$ic<=$ic_max) {
   $buffer = fgets($handle, 4096);
   echo $buffer."<br>";
}
fclose($handle);
?>

It echos the rows while it is reading the file so it is good for long files like logs.

Borgonovo

down

ecvej ¶

8 years ago


I would have expected the same behaviour from these bits of code:-

<?php

/*This times out correctly*/
while (!feof($fp)) {
    echo fgets($fp);
}

/*This times out before eof*/
while ($line=fgets($fp)) {
    echo $line;
}

/*A reasonable fix is to set a long timeout*/
stream_set_timeout($fp, 180);
while ($line=fgets($fp)) {
    echo $line;
}
?>

down

dandrews OVER AT 3dohio DOT com ¶

9 years ago


Saku's example may also be used like this:

<?php
 @ $pointer = fopen("$DOCUMENT_ROOT/foo.txt", "r"); // the @ suppresses errors so you have to test the pointer for existence
   if ($pointer) {
     while (!feof($pointer)) {
         $preTEXT = fgets($pointer, 999);
         // $TEXT .= $preTEXT;  this is better for a string
        $ATEXT[$I] = $preTEXT;  // maybe better as an array
        $I++;
     }
     fclose($pointer);
   }
?>

down

angelo [at] mandato <dot> com ¶

9 years ago


Sometimes the strings you want to read from a file are not separated by an end of line character.  the C style getline() function solves this.  Here is my version:
<?php
function getline( $fp, $delim )
{
    $result = "";
    while( !feof( $fp ) )
    {
        $tmp = fgetc( $fp );
        if( $tmp == $delim )
            return $result;
        $result .= $tmp;
    }
    return $result;
}

// Example:
$fp = fopen("/path/to/file.ext", 'r');
while( !feof($fp) )
{
    $str = getline($fp, '|');
    // Do something with $str
}
fclose($fp);
?>

down

lelkesa ¶

9 years ago


Note that - afaik - fgets reads a line until it reaches a line feed (\\n). Carriage returns (\\r) aren't processed as line endings.
However, nl2br insterts a <br /> tag before carriage returns as well.
This is useful (but not nice - I must admit) when you want to store a more lines in one.
<?php
function write_lines($text) {
  $file = fopen('data.txt', 'a');
  fwrite($file, str_replace("\n", ' ', $text)."\n");
  fclose($file);
}

function read_all() {
  $file = fopen('data.txt', 'r');
  while (!feof($file)) {
    $line = fgets($file);
    echo '<u>Section</u><p>nl2br'.($line).'</p>';
  }
  fclose($file);
}
?>

Try it.

down

Anonymous ¶

9 years ago


If you need to simulate an un-buffered fgets so that stdin doesnt hang there waiting for some input (i.e. it reads only if there is data available) use this :
<?php

    function fgets_u($pStdn) {

            $pArr = array($pStdn);

        if (false === ($num_changed_streams = stream_select($pArr, $write = NULL, $except = NULL, 0))) {
            print("\$ 001 Socket Error : UNABLE TO WATCH STDIN.\n");
            return FALSE;
        } elseif ($num_changed_streams > 0) {
                return trim(fgets($pStdn, 1024));
        }
            
    }

?>

down

timr ¶

10 years ago


If you need to read an entire file into a string, use file_get_contents().  fgets() is most useful when you need to process the lines of a file separately.

down

Pete ¶

10 years ago


If you have troubles reading binary data with versions <= 4.3.2 then upgrade to 4.3.3
The binary safe implementation seems to have had bugs which were fixed in 4.3.3

down

-1

dan at censornet dot com ¶

2 years ago


WARNING! fgets() and I presume any read() call to a file handle, e.g.

  while(!feof(STDIN)) {
    $line = fgets(STDIN);

    ...do something useful with $line...
  }

...will result in a timeout after a default time of 60 seconds on my install. This behavior is non standard (not POSIX like) and seems to me to be a bug, or if not a major caveat which should be documented more clearly.

After the timeout fgets() will return FALSE (=== FALSE), however, you can check to see if the stream (file handle) has really closed by checking feof($stream), e.g.

  while(!feof(STDIN)) {
    $line = fgets(STDIN);

    if($line === FALSE) {
      if(feof(STDIN)) {
        break;
      }
      continue;
    }
  
    ...do something useful with $line...
  }

down

-2

apardo at NOSPAM dot gmail dot com ¶

2 years ago


This is a a simple function to detect end of line type for any file.

<?php 
function detectEndOfLine($file)
{
    $handle = @fopen($file, "r");
    if ($handle)
    {
        $char=0;
        while (!$eol || feof($handle))
        {
            $char++;
            $line = fgets($handle, $char);
            $eol = preg_match("/(\r)+/", $line)? "W" : "";
            if(!$eol) $eol = preg_match("/(\n)+/", $line)? "L" : "";
        }
        return $eol;
        fclose($handle);
    }
}
?>

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