在Python中查询块设备文件的大小 [英] Query size of block device file in Python

问题描述

我有一个Python脚本，该脚本读取(通常从光学介质读取)标记不可读扇区的文件，以允许重新尝试在其他光学读取器上读取所述不可读扇区.

I have a Python script that reads a file (typically from optical media) marking the unreadable sectors, to allow a re-attempt to read said unreadable sectors on a different optical reader.

我发现我的脚本不适用于块设备(例如/dev/sr0)，以便创建包含的ISO9660/UDF文件系统的副本，因为os.stat().st_size为零.该算法目前需要提前知道文件大小；我可以更改它，但是问题(知道块设备的大小)仍然存在，并且这里没有回答，所以我打开了这个问题.

I discovered that my script does not work with block devices (e.g. /dev/sr0), in order to create a copy of the contained ISO9660/UDF filesystem, because os.stat().st_size is zero. The algorithm currently needs to know the filesize in advance; I can change that, but the issue (of knowing the block device size) remains, and it's not answered here, so I open this question.

我知道以下两个相关的SO问题:

I am aware of the following two related SO questions:

• 确定块设备的大小(/proc/partitions，通过ctypes的ioctl)
• 如何在python中检查文件大小?(关于非特殊文件)

• Determine the size of a block device (/proc/partitions, ioctl through ctypes)
• how to check file size in python? (about non-special files)

因此，我问:在Python中，如何获取块设备文件的文件大小?

Therefore, I'm asking: in Python, how can I get the file size of a block device file?

推荐答案

我达到的最干净的"(即不依赖于外部卷和最可重复使用的)Python解决方案是打开设备文件并在最后，返回文件偏移量:

The "most clean" (i.e. not dependent on external volumes and most reusable) Python solution I've reached, is to open the device file and seek at the end, returning the file offset:

def get_file_size(filename):
    "Get the file size by seeking at end"
    fd= os.open(filename, os.O_RDONLY)
    try:
        return os.lseek(fd, 0, os.SEEK_END)
    finally:
        os.close(fd)

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