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feof判断到结尾了 fgets还是获取一行空的 导致多读取一行
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feof
(PHP 4, PHP 5)
feof — 测试文件指针是否到了文件结束的位置
说明 ¶
bool feof ( resource
$handle )测试文件指针是否到了文件结束的位。
参数 ¶
handle文件指针必须是有效的，必须指向由 fopen() 或 fsockopen() 成功打开的文件(并还未由 fclose() 关闭)。
返回值 ¶
如果文件指针到了 EOF 或者出错时则返回 TRUE，否则返回一个错误（包括 socket 超时），其它情况则返回 FALSE。
注释 ¶
Warning
如果服务器没有关闭由 fsockopen() 所打开的连接，feof() 会一直等待直到超时。要解决这个问题可参见以下范例：
Example #1 处理 feof() 的超时
<?php
function safe_feof($fp, &$start = NULL) {
$start = microtime(true);
return feof($fp);
}
/* $fp 的赋值是由之前 fsockopen() 打开 */
$start = NULL;
$timeout = ini_get(‘default_socket_timeout‘);
while(!safe_feof($fp, $start) && (microtime(true) - $start) < $timeout)
{
/* Handle */
}
?>Warning
如果传递的文件指针无效可能会陷入无限循环中，因为 feof() 不会返回 TRUE。
Example #2 使用无效文件指针的 feof() 例子
<?php
// 如果文件不可读取或者不存在，fopen 函数返回 FALSE
$file = @fopen("no_such_file", "r");
// 来自 fopen 的 FALSE 会发出一条警告信息并在这里陷入无限循环
while (!feof($file)) {
}
fclose($file);
?>
add a noteUser Contributed Notes 14 notes
up
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4
4 years ago
When using feof() on a TCP stream, i found the following to work (after many hours of frustration and anger):
NOTE: I used ";" to denote the end of data transmission. This can be modified to whatever the server‘s end of file or in this case, end of output character is.
<?php
$cursor = "";
$inData = "";
while(strcmp($cursor, ";") != 0) {
$cursor = fgetc($sock);
$inData.= $cursor;
}
fclose($sock);
echo($inData);
?>
Since strcmp() returns 0 when the two strings are equal, it will return non zero as long as the cursor is not ";". Using the above method will add ";" to the string, but the fix for this is simple.
<?php
$cursor = "";
$inData = "";
$cursor = fgetc($sock);
while(strcmp($cursor, ";") != 0) {
$inData.= $cursor;
}
fclose($sock);
echo($inData);
?>
I hope this helps someone.up
down
5
8 years ago
I really thought that the feof() was TRUE when the logical file pointer is a EOF.
but no !
we need to read and get an empty record before the eof() reports TRUE.
So
$fp = fopen(‘test.bin‘,‘rb‘);
while(!feof($fp)) {
$c = fgetc($fp);
// ... do something with $c
echo ftell($fp), ",";
}
echo ‘EOF!‘;
prints for two time the last byte position.
If our file length is 5 byte this code prints
0,1,2,3,4,5,5,EOF!
Because of this, you have to do another check to verify if fgetc really reads another byte (to prevent error on "do something with $c" ^_^).
To prevent errors you have to use this code
$fp = fopen(‘test.bin‘,‘rb‘);
while(!feof($fp)) {
$c = fgetc($fp);
if($c === false) break;
// ... do something with $c
}
but this is the same of
$fp = fopen(‘test.bin‘,‘rb‘);
while(($c = fgetc($fp))!==false) {
// ... do something with $c
}
Consequently feof() is simply useless.
Before write this note I want to submit this as a php bug but one php developer said that this does not imply a bug in PHP itself (http://bugs.php.net/bug.php?id=35136&edit=2).
If this is not a bug I think that this need at least to be noticed.
Sorry for my bad english.
Bye ;)up
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4
8 years ago
feof() is, in fact, reliable. However, you have to use it carefully in conjunction with fgets(). A common (but incorrect) approach is to try something like this:
<?
$fp = fopen("myfile.txt", "r");
while (!feof($fp)) {
$current_line = fgets($fp);
// do stuff to the current line here
}
fclose($fp);
?>
The problem when processing plain text files is that feof() will not return true after getting the last line of input. You need to try to get input _and fail_ before feof() returns true. You can think of the loop above working like this:
* (merrily looping, getting lines and processing them)
* fgets used to get 2nd to last line
* line is processed
* loop back up -- feof returns false, so do the steps inside the loop
* fgets used to get last line
* line is processed
* loop back up -- since the last call to fgets worked (you got the last line), feof still returns false, so you do the steps inside the loop again
* fgets used to try to get another line (but there‘s nothing there!)
* your code doesn‘t realize this, and tries to process this non-existent line (typically by doing the same actions again)
* now when your code loops back up, feof returns true, and your loop ends
There‘s two ways to solve this:
1. You can put an additional test for feof() inside the loop
2. You can move around your calls to fgets() so that the testing of feof() happens in a better location
Here‘s solution 1:
<?
$fp = fopen("myfile.txt", "r");
while(!feof($fp)) {
$current_line = fgets($fp);
if (!feof($fp)) {
// process current line
}
}
fclose($fp);
?>
And here‘s solution 2 (IMHO, more elegant):
<?
$fp = fopen("myfile.txt", "r");
$current_line = fgets($fp);
while (!feof($fp)) {
// process current line
$current_line = fgets($fp);
}
fclose($fp);
?>
FYI, the eof() function in C++ works the exact same way, so this isn‘t just some weird PHP thing...up
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2
1 year ago
Don‘t use feof to test if you have readed all data sent by the other end of the socket. As i know it would return true only when the other end closes the connection.up
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1
7 years ago
To avoid infinite loop with fgets() just use do..while statement.
<?php
if ($f = fopen(‘myfile.txt‘, ‘r‘)) do {
$line = fgets($f);
// do any stuff here...
} while (!feof($f));
fclose($f);up
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1
7 years ago
Here‘s solution 3:
<?
$fp = fopen("myfile.txt", "r");
while ( ($current_line = fgets($fp)) !== false ) {
// do stuff to the current line here
}
fclose($fp);
?>
AFAICS fgets() never returns an empty string, so we can also write:
<?
$fp = fopen("myfile.txt", "r");
while ( $current_line = fgets($fp) ) {
// do stuff to the current line here
}
fclose($fp);
?>up
down
1
2 years ago
Return values in the documentation are incorrectly stated. It says:
Returns TRUE if the file pointer is at EOF or an error occurs (including socket timeout); otherwise returns FALSE.
Correct text would be more like:
Returns FALSE if no filehandle was passed;
returns NULL if no filehandle was passed;
returns TRUE if the file pointer is at EOF or an error occurs (including socket timeout);
otherwise returns FALSE.
As an example, running the following from the commandline:
php -r ‘echo
"Empty: ".var_export(feof(), true)."\n".
"Null: ".var_export(feof(NULL), true)."\n".
"Undefined: ".var_export(feof($undef), true)."\n"
;‘
This will output:
PHP Warning: Wrong parameter count for feof() in Command line code on line 1
PHP Warning: feof(): supplied argument is not a valid stream resource in Command line code on line 1
PHP Warning: feof(): supplied argument is not a valid stream resource in Command line code on line 1
Empty: NULL
Null: false
Undefined: false
This can, as other commenters have reported, result in infinite loops and massive PHP error logfiles, if the file handle returned by fopen() is invalid for any reason.up
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1
6 years ago
Johannes: Remember note from stream_get_meta_data page: For socket streams this member [eof] can be TRUE even when unread_bytes is non-zero. To determine if there is more data to be read, use feof() instead of reading this item.
Another thing: better not rely on the "including socket timeout" part of when feof returns true. Just found program looping two days in while(!feof($fd)) fread ... with 20 seconds timeout in PHP 4.3.10.up
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0
4 years ago
Please note that feof() used with TCP-Connections, returns false as long as the connection is open.
It even returns false when there is no data available.
BTW: Using feof() with HTTP for a single request, you should always make sure that you set the HTTP-Header "Connection" to "close" and _not_ to "keep-alive".up
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0
9 years ago
if you‘re worried the file pointer is invalid, TEST IT before you go into your loop... that way it‘ll never be an infinite loop.up
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0
10 years ago
I found feof() to be a slow function when using a non-blocking connection.
The function stream_get_meta_data() returns much quicker and has a return field ‘eof‘.up
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-1
8 years ago
if you use fseek function to pos the pointer exceed the size the file,feof still return true.so note that when you use feof as the condition of while loop.up
down
-2
8 years ago
you can avoid the infinite loop and filling the error logs
by an simple if statement
Here is the example
$handle = fopen("http://xml.weather.yahoo.com/forecastrss?p=AYXX0008&u=f", "r");
$xml = "";
if ($handle)
{
while (!feof($handle))
{
$xml .= fread($handle, 128);
}
fclose($handle);
}up
down
-1
9 years ago
if you hit an feof() infinite loop, watch out for resultant humongous logs, they can cripple a site with hard disk usage limits or run up excess usage fees. add a note
feof判断到结尾了 fgets还是获取一行空的 导致多读取一行
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