zulip/tools/replace-tarball-shebang

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#!/usr/bin/env python3
from __future__ import print_function
import six
import sys
import tarfile
stdin = getattr(sys.stdin, 'buffer', sys.stdin)
stdout = getattr(sys.stdout, 'buffer', sys.stdout)
try:
progname, old_shebang, new_shebang = sys.argv
except ValueError:
sys.exit("usage: replace-tarball-shebang '#!OLDSHEBANG' '#!NEWSHEBANG' < IN.tar[.gz] > OUT.tar")
old_shebang_bytes = old_shebang.encode()
new_shebang_bytes = new_shebang.encode()
with tarfile.open(fileobj=stdin, mode='r|*') as in_tar, \
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tarfile.open(fileobj=stdout, mode='w', format=tarfile.PAX_FORMAT, pax_headers=in_tar.pax_headers) as out_tar:
for info in in_tar:
if info.isfile():
file = in_tar.extractfile(info)
assert(file is not None) # this assert convinces mypy that it's okay to do file.read()
data = file.read()
if data.startswith(old_shebang_bytes + b' ') or data.startswith(old_shebang_bytes + b'\n'):
print('editing', info.name, file=sys.stderr)
assert info.size == len(data)
data = new_shebang_bytes + data[len(old_shebang_bytes):]
info.size = len(data)
out_tar.addfile(info, six.BytesIO(data))
else:
out_tar.addfile(info)