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68 lines
2.3 KiB
Python
68 lines
2.3 KiB
Python
#!/usr/bin/env python3
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#
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# This script is in the public domain
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#
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# Author: Johannes Schauer Marin Rodrigues <josch@mister-muffin.de>
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#
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# This script accepts a tarball on standard input and prints a tarball on
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# standard output with the same contents but all uid and gid ownership
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# information shifted by the value given as first command line argument.
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#
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# A tool like this should be written in C but libarchive has issues:
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# https://github.com/libarchive/libarchive/issues/587
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# https://github.com/libarchive/libarchive/pull/1288/ (needs 3.4.1)
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# Should these issues get fixed, then a good template is tarfilter.c in the
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# examples directory of libarchive.
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#
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# We are not using Perl either, because Archive::Tar slurps the whole tarball
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# into memory.
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#
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# We could also use Go but meh...
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# https://stackoverflow.com/a/59542307/784669
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import tarfile
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import sys
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import argparse
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def main():
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parser = argparse.ArgumentParser(
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description="""\
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Accepts a tarball on standard input and prints a tarball on standard output
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with the same contents but all uid and gid ownership information shifted by the
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value given as first command line argument.
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"""
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)
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parser.add_argument(
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"idshift",
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metavar="NUM",
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type=int,
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help="Integer value by which to shift the uid and gid of each entry",
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)
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args = parser.parse_args()
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# starting with Python 3.8, the default format became PAX_FORMAT, so this
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# is only for compatibility with older versions of Python 3
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with tarfile.open(fileobj=sys.stdin.buffer, mode="r|*") as in_tar, tarfile.open(
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fileobj=sys.stdout.buffer, mode="w|", format=tarfile.PAX_FORMAT
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) as out_tar:
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for member in in_tar:
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if args.idshift < 0 and -args.idshift > member.uid:
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print("uid cannot be negative", file=sys.stderr)
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exit(1)
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if args.idshift < 0 and -args.idshift > member.gid:
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print("gid cannot be negative", file=sys.stderr)
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exit(1)
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member.uid += args.idshift
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member.gid += args.idshift
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if member.isfile():
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with in_tar.extractfile(member) as file:
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out_tar.addfile(member, file)
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else:
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out_tar.addfile(member)
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if __name__ == "__main__":
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main()
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