我有一个使用exec()运行的命令,它从一个非常大的数据文件中返回一个值,但它必须运行数百万次。为了避免每次在循环中打开文件,我想转移到基于proc_open
的解决方案,其中文件指针创建一次以提高效率,但无法解决如何执行此操作。
这是基于exec
的版本,虽然有效但速度很慢,可能是因为它必须在每次迭代中打开文件:
foreach ($locations as $location) {
$command = "gdallocationinfo -valonly -wgs84 datafile.img {$location['lon']} {$location['lat']}";
echo exec ($command);
}
我对基于proc_open
的代码的尝试如下:
$descriptorspec = array (
0 => array ('pipe', 'r'), // stdin - pipe that the child will read from
1 => array ('pipe', 'w'), // stdout - pipe that the child will write to
// 2 => array ('file', '/tmp/errors.txt', 'a'), // stderr - file to write to
);
$command = "gdallocationinfo -valonly -wgs84 datafile.img";
$fp = proc_open ($command, $descriptorspec, $pipes);
foreach ($locations as $location) {
fwrite ($pipes[0], "{$location['lon']} {$location['lat']}\n");
fclose ($pipes[0]);
echo stream_get_contents ($pipes[1]);
fclose ($pipes[1]);
}
proc_close ($fp);
这正确获取第一个值,但随后为每个后续迭代生成错误:
3.3904595375061
Warning: fwrite(): 6 is not a valid stream resource in file.php on line 11
Warning: fclose(): 6 is not a valid stream resource in file.php on line 12
Warning: stream_get_contents(): 7 is not a valid stream resource in file.php on line 13
Warning: fclose(): 7 is not a valid stream resource in file.php on line 14
Warning: fwrite(): 6 is not a valid stream resource in file.php on line 11
...
答案 0 :(得分:0)
proc_open()
或其他任何内容解决此问题。在下面的块中,您关闭了流程的输入和输出管道,但是当您无法再读取或写入时,您会感到惊讶吗?
foreach ($locations as $location) {
fwrite ($pipes[0], "{$location['lon']} {$location['lat']}\n");
fclose ($pipes[0]); // here
echo stream_get_contents ($pipes[1]);
fclose ($pipes[1]); // and here
}
尝试不这样做。