使用 phpseclib 从 SFTP 中的大文件中获取最后 15 行 [英] Get last 15 lines from a large file in SFTP with phpseclib

问题描述

我想从使用 PHP 的 SFTP 服务器的大文件 (30MB) 中获取最后 15 行.

I want to get the last 15 lines from a large file (30MB) from a SFTP server using PHP.

我尝试像这样使用 phpseclib 的 SFTP 功能:

I tried using the phpseclib's SFTP functionality like that:

include('./Net/SFTP.php');
$sftp = new Net_SFTP("server", 2022);
if (!$sftp->login('username', 'password')) {
    exit("Login error");
}
$size = $sftp->size('./file.txt');
$Container = nl2br($sftp->get('./file.txt', false, $size - 5000));
if( !empty($Container) ) {
    echo $Container;
} else {
    exit("empty file");
}

但是对于我的大文件，这仍然需要 2 分钟才能加载.

But this still loads in like 2 minutes for my large file.

是否可以只从大文件中获取最后 X 行?

Is it possible to get only the last X lines from a large file?

推荐答案

以下内容应生成距文件末尾至少 15 行的文本块，然后您可以使用现有逻辑进一步处理.您可能需要根据文件是否以尾随换行符等结尾来调整一些逻辑.

The following should result in a blob of text with at least 15 lines from the end of the file that you can then process further with your existing logic. You may want to tweak some of the logic depending on if your file ends with a trailing newline, etc.

$filename = './file.txt'

$filesize = $sftp->size($filename);
$buffersize = 4096;

$offset = $filesize; // start at the end
$result = '';
$lines = 0;

while( $offset > 0 && $lines < 15 ) {
  // work backwards
  if( $offset < $buffersize ) {
    $offset = 0;
  } else {
    $offset -= $buffer_size;
  }
  $buffer = $sftp->get($filename, false, $offset, $buffer_size));
  // count the number of newlines as we go
  $lines += substr_count($buffer, "\n");
  $result = $buffer . $result;
}

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