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(PHP 4, PHP 5)
fgets — Liest eine Zeile von der Position des Dateizeigers
Gibt eine Zeile bis zu length -1 Bytes Länge zurück, welche aus der Datei von der aktuellen Position des Dateizeigers handle aus ausgelesen wird. Die Zeile endet an einem Zeilenumbruch (welcher im Rückgabewert enthalten ist), EOF (Ende der Datei) oder bei length - 1 Bytes (je nachdem, was eher auftritt). Ist keine Länge angegeben, wird diese auf 1k bzw. 1024 Bytes gesetzt.
Wenn ein Fehler auftritt, wird FALSE zurückgegeben.
Häufig auftretende Fehler:
Wenn Sie an die C-Semantik von fgets() gewöhnt sind, sollten Sie auf die unterschiedliche Behandlung von EOF (genauer: wie EOF zurückgegeben wird) achten.
Der Datei-Zeiger fp muss gültig sein, d.h. die Datei, auf die gezeigt wird, muss zuvor mit fopen(), popen(), oder fsockopen() geöffnet worden sein.
Ein einfaches Beispiel:
Beispiel #1 Eine Datei Zeile für Zeile einlesen
$handle = fopen ("/tmp/inputfile.txt", "r");
while (!feof($handle)) {
$buffer = fgets($handle, 4096);
echo $buffer;
}
fclose ($handle);
Hinweis: Der Parameter length wurde in PHP 4.2.0 optional. Ist er nicht angegeben, wird als Zeilenlänge 1024 angenommen. Seit PHP 4.3 wird bei einem fehlenden Parameter length so lange gelesen, bis das Ende der Zeile erreicht ist. Ist der Großteil der Zeilen in der Datei größer als 8 kB, ist es effizienter, wenn Sie die maximale Zeilenlänge spezifizieren.
Hinweis: Diese Funktion ist seit PHP 4.3 "binary safe", was aus frühere Versionen nicht zutrifft.
Hinweis: Wenn Sie Probleme damit haben, dass PHP Zeilenendezeichen nicht erkennt, entweder beim Lesen von Dateien auf einem Macintosh oder bei Dateien, die auf einem Macintosh erstellt wurden, können Sie die Option auto_detect_line_endings aktivieren.
Siehe auch fread(), fopen(), popen(), fgetc(), fsockopen() und socket_set_timeout().
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.
To have fgets get data from a (for instance binary) string this might be of help:
<?php
$data = "the string data\nyou wish\nto parse";
$fp = fopen('data:text/plain,'. $data,'rb');
while ( ($line = fgets($fp)) !== false) {
echo "$line<br>";
}
?>
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);
?>
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 $fh is undefined (i.e., "filename" does not exist). If that happens, it will keep attempting to read from a nonexistent filehandle until the process can be administratively killed or the server hangs, whichever comes first.
As I noted in a comment on stream_get_line() page, fgets is *not* necessarily slower than stream_get_line(). In my case, it's actually ~2.5 times slower. (25 seconds vs 10 seconds)
Also, stream_get_line() doesn't return the limiter. Since you pass both a maximum string length, you have no way of knowing whether or not the limiter was present in the original file, other than the 1 in 1024 chance that the line (with limiter) is exactly 1024 characters long, and appending the limiter (EG: "\n") in the case where the line is less than 1024 chars.
This latter bit compromises data integrity, stream_get_line() should probably not be used for all but very special cases.
Here my solution for the \" problem [in CSV files. This function uses fgets(), not fgetcsv().]
<?php
define("CSV_Start", 0);
define("CSV_Quoted", 1);
define("CSV_Quoted2", 2);
define("CSV_Unquoted", 3);
function readCSV($fh, $len, $delimiter = ',', $enclosure = '"') {
$data = Array();
$fildNr = 0;
$state = CSV_Start;
$data[0] = "";
do {
$line = fgets($fh, $len);
for ($ix = 0; $ix < strlen($line); $ix++) {
if ($line[$ix] == $delimiter) {
if ($state != CSV_Quoted) {
$fildNr++;
$data[$fildNr] = "";
$state = CSV_Start;
} else {
$data[$fildNr] .= $line[$ix];
}
} elseif ($line[$ix] == $enclosure) {
if ($state == CSV_Start) {
$state = CSV_Quoted;
} elseif ($state == CSV_Quoted) {
$state = CSV_Quoted2;
} elseif ($state == CSV_Quoted2) {
$data[$fildNr] .= $line[$ix];
$state = CSV_Quoted;
} else {
$data[$fildNr] .= $line[$ix];
}
} else {
$data[$fildNr] .= $line[$ix];
if ($state == CSV_Quoted2) {
echo "error";
} elseif ($state == CSV_Start) {
$state = CSV_Unquoted;
}
}
}
} while ($state == CSV_Quoted);
return $data;
}
?>
As fgets uses char(10) LF as separator instead of ch(13) CF is caused me problem in using the read value(e.g. "XYZ\n" in system() command(e.g. system("XYZ\n option") was interpreted as only system("XYZ") due to \n). \n would have to striped out first.
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
I ran into an issue that took me forever to finally figure out today, and I wanted to post my findings here in case anyone else ever runs into the same thing. I had tried to open a connection using fsockopen to my own server, send some data with fwrite, and then read the response with fgets. The data I sent over included the session ID, which was to be loaded by the page receiving it. Keep in mind that both the sender and receiver URLs were on my same server, and both tried to use the same session ID.
I found that I could do the fwrite part just fine, but that fgets would lock up indefinitely, ignoring any timeout I had set with fsockopen (but thankfully still obeying the max_execution_time limit).
The problem was that while the sending page was trying to do the fgets, it still had the session open. But the receiving page needed session data before it was willing to output anything, thereby creating a deadlock.
The solution I found was to call session_write_close() just prior to sending the request in the sender page, thereby granting access for the receiver to open up the session variables it needed.
Reply to Jerem's note. fgets terminating on chr(10) is correct.
For the sake of you youngsters who have never heard of such things, the protocol for the CRLF pair dates back to the days where the input/output with computers was on teletype machines. A sort of glorified typewriter.
chr(13) is a carriage return (CR), a command which physically moved the type head to the home position and chr(10) is a line feed (LF), which moved the paper up a line.
The standard order in which these were used was CRLF - chr(13)/chr(10) - and both were needed for a line break. Use a CR chr(13) on its own and you would overwrite the beginning of the same line. (Incidentally, this was how bold type was done - print the same thing in the same place twice!). Use LF chr(10) on its own and you would continue printing at the current position across the page but dropped down a line. (Because the paper would move up but the print head remain where it is).
Usage of this protocol has become somewhat sloppy and ill-defined these days for both printers and monitors. Some applications expect a line feed chr(10) on its own and simply assume a carriage return, others still use both but often without observing their distinctly separate functions. So much so that it may sometimes appear that they both do more or less the same thing, you only need one of them, and which to use is purely a matter of personal choice. Wrong on all counts!
fgets terminating on a LF chr(10) is correct as it ensures that the preceding CR chr(13) is included in the line if it is present - and doesn't matter if it isn't. If fgets ever terminated on CR chr(13) as jerem suggests more often than not there would be a LF at the beginning of the next line read.
The prefered use of chr(13) alone as a line break is risky. You might get away with it using your own applications and current printer, but if your file is for general release other people would see the entire output of your file printed on the same line if they use applications that interpret the CRLF pair more correctly. Not what you intended!
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.
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.
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);
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($fh);
}
fscanf($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)
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".
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.
fgets is SLOW for scanning through large files. If you don't have PHP 5, use fscanf($file, "%s\n") instead.
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;
}
?>
Macintosh line endings mentioned in docs refer to Mac OS Classic. You don't need this setting for interoperability with unixish OS X.
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
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;
}
?>
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);
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");
}
}
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);
}
?>
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);
?>
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.
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));
}
}
?>
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.
As a beginner I would have liked to see "how to read a file into a string for use later and not only how to directly echo the fgets() result. This is what I derived:
<?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 = $TEXT . $preTEXT;
}
fclose($pointer);
}
?>
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
For all those people struggling with Macintosh conversions, since PHP 4.3 there is a new runtime setting available:
auto_detect_line_endings boolean
When turned on, PHP will examine the data read by fgets() and file() to see if it is using Unix, MS-Dos or Macintosh line-ending conventions.
This enables PHP to interoperate with Macintosh systems, but defaults to Off, as there is a very small performance penalty when detecting the EOL conventions for the first line, and also because people using carriage-returns as item separators under Unix systems would experience non-backwards-compatible behaviour.
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