'archiving symlinks with python zipfile

I have a script that creates zip files of dirs containing symlinks. I was surprised to find that the zipfiles have zipped the targets of the links as opposed to the links themselves, which is what I wanted and expected. Anyone know how to get zipfile to zip the links?

Solution 1:^[1]

zipfile doesn't appear to support storing symbolic links. The way to store them in a ZIP is actually not part of the format and is only available as a custom extension in some implementations. In particular, Info-ZIP's implementation supports them so you can delegate to it instead. Make sure your decompression software can handle such archives - as I said, this feature is not standardized.

Solution 2:^[2]

It is possible to have zipfile store symbolic links, instead of the files themselves. For an example, see here. The relevant part of the script is storing the symbolic link attribute within the zipinfo:

zipInfo = zipfile.ZipInfo(archiveRoot)
zipInfo.create_system = 3
# long type of hex val of '0xA1ED0000L',
# say, symlink attr magic...
zipInfo.external_attr = 2716663808L
zipOut.writestr(zipInfo, os.readlink(fullPath))

Solution 3:^[3]

I have defined the following method in a Zip support class

def add_symlink(self, link, target, permissions=0o777):
    self.log('Adding a symlink: {} => {}'.format(link, target))
    permissions |= 0xA000

    zi = zipfile.ZipInfo(link)
    zi.create_system = 3
    zi.external_attr = permissions << 16
    self.zip.writestr(zi, target)

Solution 4:^[4]

Please find a complete Python code as a working example that creates a cpuinfo.zip archive with the symbolic link cpuinfo.txt that points to /proc/cpuinfo.

#!/usr/bin/python

import stat
import zipfile

def create_zip_with_symlink(output_zip_filename, link_source, link_target):
    zipInfo  = zipfile.ZipInfo(link_source)
    zipInfo.create_system = 3 # System which created ZIP archive, 3 = Unix; 0 = Windows
    unix_st_mode = stat.S_IFLNK | stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR | stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP | stat.S_IROTH | stat.S_IWOTH | stat.S_IXOTH
    zipInfo.external_attr = unix_st_mode << 16 # The Python zipfile module accepts the 16-bit "Mode" field (that stores st_mode field from struct stat, containing user/group/other permissions, setuid/setgid and symlink info, etc) of the ASi extra block for Unix as bits 16-31 of the external_attr
    zipOut = zipfile.ZipFile(output_zip_filename, 'w', compression=zipfile.ZIP_DEFLATED)
    zipOut.writestr(zipInfo, link_target)
    zipOut.close()

create_zip_with_symlink('cpuinfo.zip', 'cpuinfo.txt', '/proc/cpuinfo')

You can further issue the following commands (e.g. under Ubuntu) to see how the archive unpacks to a working symbolic link:

unzip cpuinfo.zip
ls -l cpuinfo.txt
cat cpuinfo.txt

Solution 5:^[5]

While not part of the POSIX standard, many zip implementations support storing generic filesystem attributes on entries. The high bytes of the 4-byte value represent the file mode.

Essentially you need to replicate ZipInfo.from_file, but without following the link or truncating the mode:

st = os.lstat(path)
mtime = time.localtime(st.st_mtime)
info = zipfile.ZipInfo(name, mtime[0:6])
info.file_size = st.st_size
info.external_attr = st.st_mode << 16
out_zip.writestr(info, os.readlink(path))

Sources

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Source: Stack Overflow

Solution	Source
Solution 1	Community
Solution 2	MuertoExcobito
Solution 3	Cameron Lowell Palmer
Solution 4
Solution 5

'archiving symlinks with python zipfile

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Solution 4:[4]

Solution 5:[5]