Is there a safe way to run a diff on two zip compressed files?

Question

Seems this would not be a deterministic thing, or is there a way to do this reliably?

Answer 1

A python solution for zip files:

import difflib
import zipfile

def diff(filename1, filename2):
    differs = False

    z1 = zipfile.ZipFile(open(filename1))
    z2 = zipfile.ZipFile(open(filename2))
    if len(z1.infolist()) != len(z2.infolist()):
        print "number of archive elements differ: {} in {} vs {} in {}".format(
            len(z1.infolist()), z1.filename, len(z2.infolist()), z2.filename)
        return 1
    for zipentry in z1.infolist():
        if zipentry.filename not in z2.namelist():
            print "no file named {} found in {}".format(zipentry.filename,
                                                        z2.filename)
            differs = True
        else:
            diff = difflib.ndiff(z1.open(zipentry.filename),
                                 z2.open(zipentry.filename))
            delta = ''.join(x[2:] for x in diff
                            if x.startswith('- ') or x.startswith('+ '))
            if delta:
                differs = True
                print "content for {} differs:\n{}".format(
                    zipentry.filename, delta)
    if not differs:
        print "all files are the same"
        return 0
    return 1

Use as

diff(filename1, filename2)

It compares files line-by-line in memory and shows changes.