# gzseek

(PHP 4, PHP 5, PHP 7)

gzseek — Seek on a gz-file pointer

### 说明

gzseek ( resource `$zp` , int `$offset` [, int `$whence` = SEEK_SET ] ) : int

Sets the file position indicator for the given file pointer to the given offset byte into the file stream. Equivalent to calling (in C) gzseek(zp, offset, SEEK_SET).

If the file is opened for reading, this function is emulated but can be extremely slow. If the file is opened for writing, only forward seeks are supported; gzseek() then compresses a sequence of zeroes up to the new starting position.

### 参数

`zp`

  The gz-file pointer. It must be valid, and must point to a file successfully opened by gzopen().

`offset`

  The seeked offset.

`whence`

  `whence` values are:

  - `SEEK_SET` - Set position equal to `offset` bytes.
  - `SEEK_CUR` - Set position to current location plus `offset`.

  If `whence` is not specified, it is assumed to be `SEEK_SET`.

### 返回值

Upon success, returns 0; otherwise, returns -1. Note that seeking past EOF is not considered an error.

### 范例

Example #1 gzseek() example

    <?php
    $gz = gzopen('somefile.gz', 'r');
    gzseek($gz,2);
    echo gzgetc($gz);
    gzclose($gz);
    ?>

### 参见

- gztell() - Tell gz-file pointer read/write position
- gzrewind() - Rewind the position of a gz-file pointer