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fgets

(PHP 4, PHP 5, PHP 7)

fgets — 从文件指针中读取一行

说明

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

从文件指针中读取一行。

参数

handle: 文件指针必须是有效的，必须指向由 fopen() 或 fsockopen() 成功打开的文件(并还未由 fclose() 关闭)。
length: 从 handle 指向的文件中读取一行并返回长度最多为 length - 1 字节的字符串。碰到换行符（包括在返回值中）、EOF 或者已经读取了 length - 1 字节后停止（看先碰到那一种情况）。如果没有指定 length，则默认为 1K，或者说 1024 字节。

Note:

从 PHP 4.3 开始，忽略掉 length 则行的长度被假定为 1024，将继续从流中读取数据直到行结束。如果文件中的大多数行都大于 8KB，则在脚本中指定最大行的长度在利用资源上更为有效。

返回值

从指针 handle 指向的文件中读取了 length - 1 字节后返回字符串。如果文件指针中没有更多的数据了则返回 FALSE 。

错误发生时返回 FALSE 。

更新日志

版本	说明
4.3.0	fgets() 开始二进制安全
4.2.0	`length` 参数成为可选。

范例

Example #1 逐行读取文件

  <?php
$handle  = @ fopen ( "/tmp/inputfile.txt" ,  "r" );
if ( $handle ) {
    while (( $buffer  =  fgets ( $handle ,  4096 )) !==  false ) {
        echo  $buffer ;
    }
    if (! feof ( $handle )) {
        echo  "Error: unexpected fgets() fail\n" ;
    }
     fclose ( $handle );
}
 ?>

注释

Note: 在读取在 Macintosh 电脑中或由其创建的文件时，如果 PHP 不能正确的识别行结束符，启用运行时配置可选项 auto_detect_line_endings 也许可以解决此问题。

Note:

习惯了 C 语言中 fgets() 语法的人应该注意到 EOF 是怎样被返回的。

参见

fgetss() - 从文件指针中读取一行并过滤掉 HTML 标记
fread() - 读取文件（可安全用于二进制文件）
fgetc() - 从文件指针中读取字符
stream_get_line() - 从资源流里读取一行直到给定的定界符
fopen() - 打开文件或者 URL
popen() - 打开进程文件指针
fsockopen() - 打开一个网络连接或者一个Unix套接字连接
stream_set_timeout() - Set timeout period on a stream

用户评论:

[#1] alex at alex-at dot ru [2015-11-03 10:28:20]

For anyone who wants a proper non-blocking fgets for sockets, there is a tiny snippet that does just that (performance should be horrible compared to fgets though):

<?php function read_line_nb($handle) { static $buffer = ''; static $lastOffset = 0; $buffer .= fread($handle, 0x1000); if (preg_match('#\\R#', $buffer, $m, PREG_OFFSET_CAPTURE, $lastOffset)) { $line = substr($buffer, 0, $m[0][1] + strlen($m[0][0])); $buffer = substr($buffer, $m[0][1] + strlen($m[0][0])); return $line; } $lastOffset = strlen($buffer); return false; } ?>

[#2] Leigh Purdie [2015-04-08 03:03:55]

A better example, to illustrate the differences in speed for large files, between fgets and stream_get_line.

This example simulates situations where you are reading potentially very long lines, of an uncertain length (but with a maximum buffer size), from an input source.

As Dade pointed out, the previous example I provided was much to easy to pick apart, and did not adequately highlight the issue I was trying to address.

Note that specifying a definitive end-character for fgets (ie: newline), generally decreases the speed difference reasonably significantly.

#!/usr/bin/php
<?php $plaintext=file_get_contents('http://loripsum.net/api/60/verylong/plaintext'); # Should be around 90k characters $plaintext=str_replace("\n"," ",$plaintext); # Get rid of newlines $fp=fopen("/tmp/SourceFile.txt","w"); for($i=0;$i<100000;$i++) { fputs($fp,substr($plaintext,0,rand(4096,65534)) . "\n"); } fclose($fp); $fp=fopen("/tmp/SourceFile.txt","r"); $start=microtime(true); while($line=fgets($fp,65535)) { 1; } $end=microtime(true); fclose($fp); $delta1=($end - $start); $fp=fopen("/tmp/SourceFile.txt","r"); $start=microtime(true); while($line=stream_get_line($fp,65535)) { 1; } $end=microtime(true); fclose($fp); $delta2=($end - $start); $pdiff=$delta1/$delta2; print "stream_get_line is " . ($pdiff>1?"faster":"slower") . " than fgets - pdiff is $pdiff\n"; ?>

$ ./testcase.php
stream_get_line is faster than fgets - pdiff is 1.760398041785

Note that, in a vast majority of situations in which php is employed, tiny differences in speed between system calls are of negligible importance.

[#3] wojons [2014-01-29 11:32:19]

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.

[#4] Anonymous [2014-01-29 11:31:27]

[#5] Dade Brandon [2013-08-31 00:33:59]

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

[#6] apardo at NOSPAM dot gmail dot com [2012-05-17 16:03:35]

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); } } ?>

[#7] dan at censornet dot com [2012-04-25 12:42:37]

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...
  }

[#8] hgs at cs dot columbia dot edu [2011-01-20 04:42:49]

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.

[#9] lzsiga at freemail.c3.hu [2010-06-04 11:32:37]

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); ?>

[#10] afwxkat at gmail dot com [2009-07-22 17:07:53]

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.

[#11] Leigh Purdie [2008-10-12 23:14:56]

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

[#12] jerem-NoSpam-ified at live dot com [2008-04-17 20:22:43]

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.

[#13] Daniel Klein [2008-01-25 08:47:11]

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.

[#14] david_sitller at blackbit dot de [2007-10-24 17:32:24]

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);

[#15] anacreo has gmail [2007-09-18 14:15:53]

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);
   }

[#16] Peter Schlaile [2007-08-21 11:36:50]

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)

[#17] David at Weintraub.name [2007-07-10 14:23:32]

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".

[#18] d at foo.com [2006-08-13 01:03:49]

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.

[#19] svayn at yahoo dot com [2006-07-14 14:21:26]

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

[#20] sam dot bryan at montal dot com [2006-05-23 02:09:55]

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; } ?>

[#21] [2006-03-24 09:36:57]

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

[#22] tavernadelleidee[italy] [2006-03-09 03:44:02]

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

[#23] ecvej [2006-01-04 13:20:42]

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

<?php while (!feof($fp)) { echo fgets($fp); } while ($line=fgets($fp)) { echo $line; } stream_set_timeout($fp, 180); while ($line=fgets($fp)) { echo $line; } ?>

[#24] hackajar <matt> yahoo <trot> com [2005-12-05 12:17:48]

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);

[#25] kpeters AT-AT monolithss DEE OH TEE com [2005-12-01 05:51:45]

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");
  }
}

[#26] dandrews OVER AT 3dohio DOT com [2005-01-07 11:11:53]

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); } ?>

[#27] angelo [at] mandato <dot> com [2004-11-19 06:43:56]

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); ?>

[#28] lelkesa [2004-11-04 02:54:03]

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.

[#29] [2004-09-05 15:05:28]

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)); } } ?>

[#30] timr [2004-06-16 19:13:22]

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.

[#31] Pete [2004-02-22 16:35:36]

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