fgetcsv
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.
fgets
(PHP 4, PHP 5)
fgets — Gets line from file pointer
Description
string fgets
( resource $handle
[, int $length
] )
Gets a line from file pointer.
Parameters
- handle
-
The file pointer must be valid, and must point to a file successfully opened by fopen() or fsockopen() (and not yet closed by fclose()).
- length
-
Reading ends when length - 1 bytes have been read, on a newline (which is included in the return value), or on EOF (whichever comes first). If no length is specified, it will keep reading from the stream until it reaches the end of the line.
Note: Until PHP 4.3.0, omitting it would assume 1024 as the line length. If the majority of the lines in the file are all larger than 8KB, it is more resource efficient for your script to specify the maximum line length.
Return Values
Returns a string of up to length - 1 bytes read from the file pointed to by handle .
If an error occurs, returns FALSE.
ChangeLog
| Version | Description |
|---|---|
| 4.3.0 | fgets() is now binary safe |
| 4.2.0 | The length parameter became optional |
Examples
Example #1 Reading a file line by line
<?php
$handle = @fopen("/tmp/inputfile.txt", "r");
if ($handle) {
while (!feof($handle)) {
$buffer = fgets($handle, 4096);
echo $buffer;
}
fclose($handle);
}
?>
Notes
Note: If PHP is not properly recognizing the line endings when reading files either on or created by a Macintosh computer, enabling the auto_detect_line_endings run-time configuration option may help resolve the problem.
Note: People used to the 'C' semantics of fgets() should note the difference in how EOF is returned.
add a note
User Contributed Notesfgets
soapergem at gmail dot com
31-Jul-2008 01:49
31-Jul-2008 01:49
julian dot chappell at NOSPAM dot btopenworld dot com
26-Jun-2008 10:14
26-Jun-2008 10:14
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!
jerem-NoSpam-ified at live dot com
18-Apr-2008 10:22
18-Apr-2008 10:22
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.
Daniel Klein
25-Jan-2008 11:47
25-Jan-2008 11:47
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.
david_sitller at blackbit dot de
25-Oct-2007 07:32
25-Oct-2007 07:32
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);
anacreo has gmail
19-Sep-2007 04:15
19-Sep-2007 04:15
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($fh);
}
Peter Schlaile
22-Aug-2007 01:36
22-Aug-2007 01:36
fscanf($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)
David at Weintraub.name
11-Jul-2007 04:23
11-Jul-2007 04:23
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".
d at foo.com
13-Aug-2006 03:03
13-Aug-2006 03:03
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.
svayn at yahoo dot com
15-Jul-2006 04:21
15-Jul-2006 04:21
fgets is SLOW for scanning through large files. If you don't have PHP 5, use fscanf($file, "%s\n") instead.
sam dot bryan at montal dot com
23-May-2006 04:09
23-May-2006 04:09
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;
}
?>
25-Mar-2006 12:36
Macintosh line endings mentioned in docs refer to Mac OS Classic. You don't need this setting for interoperability with unixish OS X.
tavernadelleidee[italy]
09-Mar-2006 06:44
09-Mar-2006 06:44
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
ecvej
05-Jan-2006 04:20
05-Jan-2006 04:20
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;
}
?>
hackajar <matt> yahoo <trot> com
06-Dec-2005 03:17
06-Dec-2005 03:17
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);
kpeters AT-AT monolithss DEE OH TEE com
01-Dec-2005 08:51
01-Dec-2005 08:51
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");
}
}
dandrews OVER AT 3dohio DOT com
08-Jan-2005 02:11
08-Jan-2005 02:11
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);
}
?>
angelo [at] mandato <dot> com
19-Nov-2004 09:43
19-Nov-2004 09:43
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);
?>
lelkesa
04-Nov-2004 05:54
04-Nov-2004 05:54
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.
06-Sep-2004 05:05
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));
}
}
?>
timr
17-Jun-2004 09:13
17-Jun-2004 09:13
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.
Saku
05-Jun-2004 07:47
05-Jun-2004 07:47
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);
}
?>
Pete
23-Feb-2004 07:35
23-Feb-2004 07:35
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