在 python 脚本中读取 tar 文件内容而不解压缩它

Question

我有一个 tar 文件，里面有很多文件。 我需要编写一个 python 脚本，它将读取文件的内容并给出总字符数，包括字母总数、空格、换行符等所有内容，而无需解压缩 tar 文件。

Answer 1

你可以使用getmembers()

>>> import  tarfile
>>> tar = tarfile.open("test.tar")
>>> tar.getmembers()

之后，您可以使用extractfile() 将成员提取为文件对象。只是一个例子

import tarfile,os
import sys
os.chdir("/tmp/foo")
tar = tarfile.open("test.tar")
for member in tar.getmembers():
    f=tar.extractfile(member)
    content=f.read()
    print "%s has %d newlines" %(member, content.count("\n"))
    print "%s has %d spaces" % (member,content.count(" "))
    print "%s has %d characters" % (member, len(content))
    sys.exit()
tar.close()

上面例子中的文件对象f，可以使用read()、readlines()等。

Answer 2

您需要使用 tarfile 模块。具体来说，您使用 TarFile 类的实例来访问文件，然后使用 TarFile.getnames() 访问名称

 |  getnames(self)
 |      Return the members of the archive as a list of their names. It has
 |      the same order as the list returned by getmembers().

如果您想阅读内容，则使用此方法

 |  extractfile(self, member)
 |      Extract a member from the archive as a file object. `member' may be
 |      a filename or a TarInfo object. If `member' is a regular file, a
 |      file-like object is returned. If `member' is a link, a file-like
 |      object is constructed from the link's target. If `member' is none of
 |      the above, None is returned.
 |      The file-like object is read-only and provides the following
 |      methods: read(), readline(), readlines(), seek() and tell()

Answer 3

之前，这篇文章展示了一个“dict(zip(()”) 将成员名称和成员列表放在一起的示例，这很愚蠢并且会导致对存档的过度读取，为了实现同样的效果，我们可以使用字典理解：

index = {i.name: i for i in my_tarfile.getmembers()}

---

更多关于如何使用 tarfile 的信息

提取一个 tarfile 成员

#!/usr/bin/env python3
import tarfile

my_tarfile = tarfile.open('/path/to/mytarfile.tar')

print(my_tarfile.extractfile('./path/to/file.png').read())

索引 tar 文件

#!/usr/bin/env python3
import tarfile
import pprint

my_tarfile = tarfile.open('/path/to/mytarfile.tar')

index = my_tarfile.getnames()  # a list of strings, each members name
# or
# index = {i.name: i for i in my_tarfile.getmembers()}

pprint.pprint(index)

索引、读取、动态额外的 tar 文件

#!/usr/bin/env python3

import tarfile
import base64
import textwrap
import random

# note, indexing a tar file requires reading it completely once
# if we want to do anything after indexing it, it must be a file
# that can be seeked (not a stream), so here we open a file we
# can seek
my_tarfile = tarfile.open('/path/to/mytar.tar')


# tarfile.getmembers is similar to os.stat kind of, it will
# give you the member names (i.name) as well as TarInfo attributes:
#
# chksum,devmajor,devminor,gid,gname,linkname,linkpath,
# mode,mtime,name,offset,offset_data,path,pax_headers,
# size,sparse,tarfile,type,uid,uname
#
# here we use a dictionary comprehension to index all TarInfo
# members by the member name
index = {i.name: i for i in my_tarfile.getmembers()}

print(index.keys())

# pick your member
# note: if you can pick your member before indexing the tar file,
# you don't need to index it to read that file, you can directly
# my_tarfile.extractfile(name)
# or my_tarfile.getmember(name)

# pick your filename from the index dynamically
my_file_name = random.choice(index.keys())

my_file_tarinfo = index[my_file_name]
my_file_size = my_file_tarinfo.size
my_file_buf = my_tarfile.extractfile( 
    my_file_name
    # or my_file_tarinfo
)

print('file_name: {}'.format(my_file_name))
print('file_size: {}'.format(my_file_size))
print('----- BEGIN FILE BASE64 -----'
print(
    textwrap.fill(
        base64.b64encode(
            my_file_buf.read()
        ).decode(),
        72
    )
)
print('----- END FILE BASE64 -----'

包含重复成员的 tar 文件

如果我们有一个奇怪创建的 tar，在这个例子中，通过将同一个文件的多个版本附加到同一个 tar 存档中，我们可以仔细处理，我已经注释了哪些成员包含哪些文本，假设我们想要第四个（索引 3）成员，“capturetheflag\n”

tar -tf mybadtar.tar 
mymember.txt  # "version 1\n"
mymember.txt  # "version 1\n"
mymember.txt  # "version 2\n"
mymember.txt  # "capturetheflag\n"
mymember.txt  # "version 3\n"

#!/usr/bin/env python3

import tarfile
my_tarfile = tarfile.open('mybadtar.tar')

# >>> my_tarfile.getnames()
# ['mymember.txt', 'mymember.txt', 'mymember.txt', 'mymember.txt', 'mymember.txt']

# if we use extracfile on a name, we get the last entry, I'm not sure how python is smart enough to do this, it must read the entire tar file and buffer every valid member and return the last one

# >>> my_tarfile.extractfile('mymember.txt').read()
# b'version 3\n'

# >>> my_tarfile.extractfile(my_tarfile.getmembers()[3]).read()
# b'capturetheflag\n'

或者，我们可以遍历 tar 文件 #!/usr/bin/env python3

import tarfile
my_tarfile = tarfile.open('mybadtar.tar')
# note, if we do anything to the tarfile object that will 
# cause a full read, the tarfile.next() method will return none,
# so call next in a loop as the first thing you do if you want to
# iterate

while True:
    my_member = my_tarfile.next()
    if not my_member:
        break
    print((my_member.offset, mytarfile.extractfile(my_member).read,))

# (0, b'version 1\n')
# (1024, b'version 1\n')
# (2048, b'version 2\n')
# (3072, b'capturetheflag\n')
# (4096, b'version 3\n')


    

Answer 4

你可以使用 tarfile.list() 例如：

filename = "abc.tar.bz2"
with open( filename , mode='r:bz2') as f1:
    print(f1.list())

获得这些数据后。您可以操作或将此输出写入文件并执行您的任何要求。