如何在磁带上写EOF标记-Python

Question

我在网上搜索了很多，但我找不到用Python在磁带上写EOF标记的方法。

我有下面的代码(通过fcntl.ioctl使用Python(，它写记录，但在每次os.write之后，它不写EOF，而是将记录保存在一个文件中。从本质上讲，我想将这些记录拆分为中间有EOF标记的文件？

代码：

import os
import struct
import fcntl
MTIOCTOP = 0x40086d01  # Do a magnetic tape operation
MTSETBLK = 20
TAPEDRIVE = '/dev/st1'
fh = os.open(TAPEDRIVE, os.O_WRONLY )
fcntl.ioctl(fh, MTIOCTOP, struct.pack('hi', MTSETBLK, 0))
os.write(fh, b'a'*1024)                                      #<- Does not add EOF mark after write
fcntl.ioctl(fh, MTIOCTOP, struct.pack('hi', MTSETBLK, 0))
os.write(fh, b'b'*2048)
fcntl.ioctl(fh, MTIOCTOP, struct.pack('hi', MTSETBLK, 0))
os.write(fh, b'c'*1024)
fcntl.ioctl(fh, MTIOCTOP, struct.pack('hi', MTSETBLK, 0))
os.write(fh, b'd'*2048)
os.close(fh)

磁带分析：

Commencing Reading Tape in Drive /dev/st1, blocksize = 32768
1024 2048 1024 2048
End of File Mark after 4 records
End of File Mark after 0 records
End of Tape
Tape Examination Complete, found 2 Files on tape`

我注意到mtio.h在这里包含MTWEOF，但我不确定如何通过ioctl实现这一点？

如有任何帮助，我们将不胜感激。

PS。我知道我可以使用mt -f /dev/st1 weof n#编写EOF标记，但我更喜欢只在Python中使用。

Answer 1

好的，所以在阅读了mtio.h手册页之后，我制定了它，希望它能对其他人有所帮助。

import os
import fcntl
import struct
MTIOCTOP    = 0x40086d01  # Do a magnetic tape operation refer to mtio.h 
#MTSETBLK   = 20          # Set a block size?
MTWEOF      = 5           # Define EOF mark variable refer to mtio.h 
TAPEDRIVE   = '/dev/st1'  # Tape drive location
fd = os.open(TAPEDRIVE, os.O_WRONLY )                          # Open device for write   
#fcntl.ioctl(fd, MTIOCTOP, struct.pack('hi', MTSETBLK, 32768)) # Set a block size?

for _ in range(5):                                            
os.write(fd, b'a'*1024)                                    # Write some bytes
fcntl.ioctl(fd, MTIOCTOP, struct.pack('hi', MTWEOF, 1))    # Write end-of-file (1)
fcntl.ioctl(fd, MTIOCTOP, struct.pack('hi', MTWEOF, 2))        # Write end-of-tape (2)
os.close(fd)

磁带分析

Commencing Reading Tape in Drive /dev/st1, blocksize = 32768
1024 1024 1024 1024 1024 
End of File Mark after 1 records
End of File Mark after 1 records
End of File Mark after 1 records
End of File Mark after 1 records
End of File Mark after 1 records
End of Tape
Tape Examination Complete, found 5 Files on tape