# SplFileObject::ftruncate

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

SplFileObject::ftruncate — Truncates the file to a given length

### 说明

public SplFileObject::ftruncate(int `$size`): bool

Truncates the file to `size` bytes.

### 参数

`size`

  The size to truncate to.

  > 注意:

  > If `size` is larger than the file it is extended with null bytes.

  > If `size` is smaller than the file, the extra data will be lost.

### 返回值

成功时返回 `true`， 或者在失败时返回 `false`。

### 示例

示例 #1 SplFileObject::ftruncate() example

`<?php
// Create file containing "Hello World!"
$file = new SplFileObject("/tmp/ftruncate", "w+");
$file->fwrite("Hello World!");
// Truncate to 5 bytes
$file->ftruncate(5);
// Rewind and read data
$file->rewind();
echo $file->fgets();
?>`

以上示例的输出类似于：

    Hello

### 参见

- ftruncate() - 将文件截断到指定的长度

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