PHP：读取大文件中的特定行（不需要逐行读取） [英] PHP: Read specific lines in a large file (without reading it line-by-line)

问题描述

  line1（数字或一个简短字符串）
 line2（可以是几个MB文字）
; 
 line1 
 line2 
; 
 line1 
 line2 
; 
 ... 
  

总文件大小超过了100MB，所以每次只读一行是相当缓慢的。
我只想读取每个块的line1，并跳过所有的line2。或者只是读一条线，我知道的linenumber。有什么办法，我可以做到这一点与PHP？读取行的标准方法是将行写入内存中，并且对于这种结构不是那么有效。

（我知道一个数据库结构会更好用，但这是）

解决方案

使用splfileobject

• 不需要逐行读取所有行

/ p>

如果您知道行号：

  //可以说你需要第4行
 $ myLine = 4; 
 $ file = new SplFileObject（'bigFile.txt'）; 
 //这是基于零的，所以需要减去1 
 $ file-> seek（$ myLine-1）; 
 //现在打印
 echo $ file-> current（）; 
  

检查：
http://www.php.net/manual/en/splfileobject.seek.php

I have this file structure:

line1 (number or a a short string)
line2 (can be several MB of text)
;
line1
line2
;
line1
line2
;
...

The total filesize is exceeding 100MB so reading it line by line each time is rather slow. I want to read only "line1" of each block and skip all the "line2". Or just read a line which I know the linenumber for. Is there any way that I can do it with php? The standard methods of reading lines takes the lines into memory and it not so effective with this structure.

(I know a database structure would be a much better use but this is a study-case that I really want an solution to.)

解决方案

Using splfileobject

• no need to read all lines 1 by 1

• can "jump" to desired line

In the case you know the line number :

//lets say you need line 4
$myLine = 4 ; 
$file = new SplFileObject('bigFile.txt');
//this is zero based so need to subtract 1
$file->seek($myLine-1);
//now print the line
echo $file->current();

check out : http://www.php.net/manual/en/splfileobject.seek.php

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