如何在PHP中只读取文本文件的最后5行？
我有一个名为如何在PHP中只读取文本文件的最后5行？,php,fopen,Php,Fopen,我有一个名为file.txt的文件，它通过添加行来更新 我通过以下代码阅读： $fp = fopen("file.txt", "r"); $data = ""; while(!feof($fp)) { $data .= fgets($fp, 4096); } echo $data; 出现了大量的线条。 我只想回显文件的最后5行 我该怎么做 file.txt如下所示： 11111111111111 22222222222 33333333333333 44444444444 5555555
file.txt$fp = fopen("file.txt", "r");
$data = "";
while(!feof($fp))
{
$data .= fgets($fp, 4096);
}
echo $data;
file.txt11111111111111
22222222222
33333333333333
44444444444
55555555555555
66666666666
如果行之间用CR或LF分隔，请尝试使用$data变量：
$lines = explode("\n", $data);
$lines应该是一个数组，您可以使用sizeof（）计算出记录的数量，只需得到最后5条。未测试的代码，但应该可以：
$file = file("filename.txt");
for ($i = max(0, count($file)-6); $i < count($file); $i++) {
echo $file[$i] . "\n";
}
$file=file（“filename.txt”）；
对于（$i=max（0，count（$file）-6）；$imax函数ReadFromEndByLine（$filename，$lines）
function ReadFromEndByLine($filename,$lines)
{
/* freely customisable number of lines read per time*/
$bufferlength = 5000;
$handle = @fopen($filename, "r");
if (!$handle) {
echo "Error: can't find or open $filename<br/>\n";
return -1;
}
/*get the file size with a trick*/
fseek($handle, 0, SEEK_END);
$filesize = ftell($handle);
/*don't want to get past the start-of-file*/
$position= - min($bufferlength,$filesize);
while ($lines > 0) {
if ($err=fseek($handle,$position,SEEK_END)) { /* should not happen but it's better if we check it*/
echo "Error $err: something went wrong<br/>\n";
fclose($handle);
return $lines;
}
/* big read*/
$buffer = fread($handle,$bufferlength);
/* small split*/
$tmp = explode("\n",$buffer);
/*previous read could have stored a partial line in $aliq*/
if ($aliq != "") {
/*concatenate current last line with the piece left from the previous read*/
$tmp[count($tmp)-1].=$aliq;
}
/*drop first line because it may not be complete*/
$aliq = array_shift($tmp);
$read = count($tmp);
if ( $read >= $lines ) { /*have read too much!*/
$tmp2 = array_slice($tmp,$read-$n);
/* merge it with the array which will be returned by the function*/
$lines = array_merge($tmp2,$lines);
/* break the cycle*/
$lines = 0;
} elseif (-$position >= $filesize) { /* haven't read enough but arrived at the start of file*/
//get back $aliq which contains the very first line of the file
$lines = array_merge($aliq,$tmp,$lines);
//force it to stop reading
$lines = 0;
} else { /*continue reading...*/
//add the freshly grabbed lines on top of the others
$lines = array_merge($tmp,$lines);
$lines -= $read;
//next time we want to read another block
$position -= $bufferlength;
//don't want to get past the start of file
$position = max($position, -$filesize);
}
}
fclose($handle);
return $lines;
}
{
/*可自由定制每次读取的行数*/
$bufferlength=5000；
$handle=@fopen（$filename，“r”）；
如果（！$handle）{
echo“错误：无法找到或打开$filename
\n”；
返回-1；
}
/*使用技巧获取文件大小*/
fseek（$handle，0，SEEK\u END）；
$filesize=ftell（$handle）；
/*不想超过文件的开头*/
$position=-min（$bufferlength，$filesize）；
而（$line>0）{
如果（$err=fseek（$handle，$position，SEEK_END））{/*不应该发生，但最好检查一下*/
echo“Error$err:出现问题
\n”；
fclose（$handle）；
返回$line；
}
/*博览群书*/
$buffer=fread（$handle，$bufferlength）；
/*小裂口*/
$tmp=explode（“\n”，$buffer）；
/*以前的读取可能在$aliq中存储了部分行*/
如果（$aliq！=“”）{
/*将当前最后一行与上一次读取的剩余部分连接起来*/
$tmp[count（$tmp）-1]。=$aliq；
}
/*删除第一行，因为它可能不完整*/
$aliq=阵列移位（$tmp）；
$read=计数（$tmp）；
如果（$read>=$line）{/*读得太多了*/
$tmp2=阵列片（$tmp，$read-$n）；
/*将其与函数返回的数组合并*/
$lines=数组合并（$tmp2，$lines）；
/*打破循环*/
$lines=0；
}elseif（-$position>=$filesize）{/*尚未读取足够的内容，但已到达文件的开头*/
//获取$aliq，它包含文件的第一行
$lines=array\u merge（$aliq、$tmp、$lines）；
//强迫它停止阅读
$lines=0；
}否则{/*继续阅读*/
//将新抓取的线条添加到其他线条之上
$lines=数组合并（$tmp，$lines）；
$lines-=$read；
//下一次我们想读另一块
$position-=$bufferlength；
//不想超过文件的开头
$position=max（$position，-$filesize）；
}
}
fclose（$handle）；
返回$line；
}
ReadFromEndByLine（'myFile.txt'，6） 对于大文件，使用file（）将所有行读入数组有点浪费。以下是如何读取文件并维护最后5行的缓冲区：
$lines=array();
$fp = fopen("file.txt", "r");
while(!feof($fp))
{
$line = fgets($fp, 4096);
array_push($lines, $line);
if (count($lines)>5)
array_shift($lines);
}
fclose($fp);
//how many lines?
$linecount=5;
//what's a typical line length?
$length=40;
//which file?
$file="test.txt";
//we double the offset factor on each iteration
//if our first guess at the file offset doesn't
//yield $linecount lines
$offset_factor=1;
$bytes=filesize($file);
$fp = fopen($file, "r") or die("Can't open $file");
$complete=false;
while (!$complete)
{
//seek to a position close to end of file
$offset = $linecount * $length * $offset_factor;
fseek($fp, -$offset, SEEK_END);
//we might seek mid-line, so read partial line
//if our offset means we're reading the whole file,
//we don't skip...
if ($offset<$bytes)
fgets($fp);
//read all following lines, store last x
$lines=array();
while(!feof($fp))
{
$line = fgets($fp);
array_push($lines, $line);
if (count($lines)>$linecount)
{
array_shift($lines);
$complete=true;
}
}
//if we read the whole file, we're done, even if we
//don't have enough lines
if ($offset>=$bytes)
$complete=true;
else
$offset_factor*=2; //otherwise let's seek even further back
}
fclose($fp);
var_dump($lines);
//有多少行？
$linecount=5；
//典型的线路长度是多少？
$length=40；
//哪个文件？
$file=“test.txt”；
//我们在每次迭代中将偏移因子加倍
//如果我们对文件偏移量的第一次猜测不正确
//产生$linecount行
$offset_系数=1；
$bytes=文件大小（$file）；
$fp=fopen（$file，“r”）或die（“无法打开$file”）；
$complete=false；
while（！$complete）
{
//搜索到靠近文件末尾的位置
$offset=$linecount*$length*$offset\u因子；
fseek（$fp，-$offset，SEEK_END）；
//我们可能会寻找中间线，所以请阅读部分线
//如果偏移量意味着我们正在读取整个文件，
//我们不会跳过。。。
如果（$offset$linecount）
{
数组移位（$行）；
$complete=true；
}
}
//如果我们读了整个文件，就算我们
//没有足够的线路
如果（$offset>=$bytes）
$complete=true；
其他的
$offset_系数*=2//否则，让我们再往回看
}
fclose（$fp）；
var_转储（行）；
$data = array_slice(file('file.txt'), -5);
foreach ($data as $line) {
echo $line;
}
如果您使用的是linux系统，则可以执行以下操作：
$lines = `tail -5 /path/to/file.txt`;
$all_lines = file('file.txt');
$last_5 = array_slice($all_lines , -5);
这是一个常见的面试问题。这是我去年被问到这个问题时写的。请记住，在堆栈溢出上获得的代码是使用许可的
我已经测试过这个了。它对我有用
function getlast($filename,$linenum_to_read,$linelength){
// this function takes 3 arguments;
if (!$linelength){ $linelength = 600;}
$f = fopen($filename, 'r');
$linenum = filesize($filename)/$linelength;
for ($i=1; $i<=($linenum-$linenum_to_read);$i++) {
$data = fread($f,$linelength);
}
echo "<pre>";
for ($j=1; $j<=$linenum_to_read+1;$j++) {
echo fread($f,$linelength);
}
echo "</pre><hr />The filesize is:".filesize("$filename");
}
getlast("file.txt",6,230);
?>
函数getlast（$filename，$linenum\u to\u read，$linelength）{
//这个函数有3个参数；
如果（！$linelength）{$linelength=600；}
$f=fopen（$filename，'r'）；
$linenum=filesize（$filename）/$linelength；
对于（$i=1；$i）
文件（）// Will seek backwards $n lines from the current position
function seekLineBackFast($fh, $n = 1){
$pos = ftell($fh);
if ($pos == 0)
return false;
$posAtStart = $pos;
$readSize = 2048*2;
$pos = ftell($fh);
if(!$pos){
fseek($fh, 0, SEEK_SET);
return false;
}
// we want to seek 1 line before the line we want.
// so that we can start at the very beginning of the line
while ($n >= 0) {
if($pos == 0)
break;
$pos -= $readSize;
if($pos <= 0){
$pos = 0;
}
// fseek returns 0 on success and -1 on error
if(fseek($fh, $pos, SEEK_SET)==-1){
fseek($fh, 0, SEEK_SET);
break;
}
$data = fread($fh, $readSize);
$count = substr_count($data, "\n");
$n -= $count;
if($n < 0)
break;
}
fseek($fh, $pos, SEEK_SET);
// we may have seeked too far back
// so we read one line at a time forward
while($n < 0){
fgets($fh);
$n++;
}
// just in case?
$pos = ftell($fh);
if(!$pos)
fseek($fh, 0, SEEK_SET);
// check that we have indeed gone back
if ($pos >= $posAtStart)
return false;
return $pos;
}
此功能将真正适用于l
<?php
function read_backward_line($filename, $lines, $revers = false)
{
$offset = -1;
$c = '';
$read = '';
$i = 0;
$fp = @fopen($filename, "r");
while( $lines && fseek($fp, $offset, SEEK_END) >= 0 ) {
$c = fgetc($fp);
if($c == "\n" || $c == "\r"){
$lines--;
if( $revers ){
$read[$i] = strrev($read[$i]);
$i++;
}
}
if( $revers ) $read[$i] .= $c;
else $read .= $c;
$offset--;
}
fclose ($fp);
if( $revers ){
if($read[$i] == "\n" || $read[$i] == "\r")
array_pop($read);
else $read[$i] = strrev($read[$i]);
return implode('',$read);
}
return strrev(rtrim($read,"\n\r"));
}
//if $revers=false function return->
//line 1000: i am line of 1000
//line 1001: and i am line of 1001
//line 1002: and i am last line
//but if $revers=true function return->
//line 1002: and i am last line
//line 1001: and i am line of 1001
//line 1000: i am line of 1000
?>
// Will seek backwards $n lines from the current position
function seekLineBackFast($fh, $n = 1){
$pos = ftell($fh);
if ($pos == 0)
return false;
$posAtStart = $pos;
$readSize = 2048*2;
$pos = ftell($fh);
if(!$pos){
fseek($fh, 0, SEEK_SET);
return false;
}
// we want to seek 1 line before the line we want.
// so that we can start at the very beginning of the line
while ($n >= 0) {
if($pos == 0)
break;
$pos -= $readSize;
if($pos <= 0){
$pos = 0;
}
// fseek returns 0 on success and -1 on error
if(fseek($fh, $pos, SEEK_SET)==-1){
fseek($fh, 0, SEEK_SET);
break;
}
$data = fread($fh, $readSize);
$count = substr_count($data, "\n");
$n -= $count;
if($n < 0)
break;
}
fseek($fh, $pos, SEEK_SET);
// we may have seeked too far back
// so we read one line at a time forward
while($n < 0){
fgets($fh);
$n++;
}
// just in case?
$pos = ftell($fh);
if(!$pos)
fseek($fh, 0, SEEK_SET);
// check that we have indeed gone back
if ($pos >= $posAtStart)
return false;
return $pos;
}
//read last 5 lines
$lines = \jasir\FileHelpers\FileHelpers::readLastLines($pathToFile, 5);
$data = array_slice(file('logs.txt'),10);
foreach ($data as $line)
{
echo $line."<br/>";
}
$lines=array();
$fp = fopen("userlog.txt", "r");
while(!feof($fp))
{
$line = fgets($fp, 4096);
array_push($lines, $line);
if (count($lines)>25)
array_shift($lines);
}
fclose($fp);
while ($a <= 10) {
$a++;
echo "<br>".$lines[$a];
}
$dosya = "../dosya.txt";
$array = explode("\n", file_get_contents($dosya));
$reversed = array_reverse($array);
for($x = 0; $x < 6; $x++)
{
echo $reversed[$x];
}
$file = new SplFileObject('large_file.txt', 'r');
$file->seek(PHP_INT_MAX);
$last_line = $file->key();
$lines = new LimitIterator($file, $last_line - 5, $last_line);
print_r(iterator_to_array($lines));
exec('tail -3 /logs/reports/2017/02-15/173606-arachni-2415.log', $output);
echo $output;
// 2017-02-15 18:03:25 [*] Path Traversal: Analyzing response ...
// 2017-02-15 18:03:27 [*] Path Traversal: Analyzing response ...
// 2017-02-15 18:03:27 [*] Path Traversal: Analyzing response ...
/**
*
* Reads N lines from a file
*
* @param type $file path
* @param type $maxLines Count of lines to read
* @param type $reverse set to true if result should be reversed.
* @return string
*/
public function readLinesFromFile($file, $maxLines, $reverse=false)
{
$lines = file($file);
if ($reverse) {
$lines = array_reverse($lines);
}
$tmpArr = array();
if ($maxLines > count($lines))
exit("\$maxLines ist größer als die Anzahl der Zeilen in der Datei.");
for ($i=0; $i < $maxLines; $i++) {
array_push($tmpArr, $lines[$i]);
}
if ($reverse) {
$tmpArr = array_reverse($tmpArr);
}
$out = "";
for ($i=0; $i < $maxLines; $i++) {
$out .= $tmpArr[$i] . "</br>";
}
return $out;
}
function readLastLines($filename, $num, $reverse = false)
{
$file = new \SplFileObject($filename, 'r');
$file->seek(PHP_INT_MAX);
$last_line = $file->key();
$lines = new \LimitIterator($file, $last_line - $num, $last_line);
$arr = iterator_to_array($lines);
if($reverse) $arr = array_reverse($arr);
return implode('',$arr);
}
// use it by
$lines = readLastLines("file.txt", 5) // return string with 5 last lines