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gzseek

(PHP 4, PHP 5, PHP 7, PHP 8)

gzseekSeek on a gz-file pointer

Description

gzseek(resource $stream, 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.

Parameters

stream

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.

Return Values

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

Examples

Example #1 gzseek() example

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

See Also

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

add a note

User Contributed Notes 2 notes

up
0
liuhaifeng at example dot com
11 years ago
Since seek after the end is not considered an error, I doubt that "while (gzseek ($fh, $eof) == 0) $eof += $d;" will get into infinite loop.
up
0
dperham at wgate dot com
18 years ago
PHP/4.3.9
contrary to the notes, gzseek() returns -1 if I try to seek past the end of the file. here is a function that will return the last seekable position, and put the file pointer there.

/** sets the file pointer at the end of the file
* and returns the number of bytes in the file.
*/
function gzend($fh)
{
$d = 1<<14;
$eof = $d;
while ( gzseek($fh, $eof) == 0 ) $eof += $d;
while ( $d > 1 )
{
$d >>= 1;
$eof += $d * (gzseek($fh, $eof)? -1 : 1);
}
return $eof;
}
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