How to DEFLATE with a command line tool to extract

Question

I'm looking for a command line wrapper for the DEFLATE algorithm.

I have a file (git blob) that is compressed using DEFLATE, and I want to uncompress it. The gzip command does not seem to have an option to directly use the DEFLATE algorithm, rather than the gzip format.

Ideally I'm looking for a standard Unix/Linux tool that can do this.

edit: This is the output I get when trying to use gzip for my problem:

$ cat .git/objects/c0/fb67ab3fda7909000da003f4b2ce50a53f43e7 | gunzip

gzip: stdin: not in gzip format

Answer 1

You can use zlib-flate, like this:

cat .git/objects/c0/fb67ab3fda7909000da003f4b2ce50a53f43e7 \
    | zlib-flate -uncompress; echo

It's there by default on my machine, but it's part of qpdf - tools for and transforming and inspecting PDF files if you need to install it.

I've popped an echo on the end of the command, as it's easier to read the output that way.

Answer 2

// save this as deflate.go

package main

import (
    "compress/zlib"
    "io"
    "os"
    "flag"
)

var infile = flag.String("f", "", "infile")

func main() {
    flag.Parse()
    file, _ := os.Open(*infile)

    r, err := zlib.NewReader(file)
    if err != nil {
        panic(err)
    }
    io.Copy(os.Stdout, r)

    r.Close()
}

---

$ go build deflate.go
$ ./deflate -f .git/objects/c0/fb67ab3fda7909000da003f4b2ce50a53f43e7

Answer 3

Here is a Ruby one-liner ( cd .git/ first and identify path to any object ):

ruby -rzlib -e 'print Zlib::Inflate.new.inflate(STDIN.read)' < ./74/c757240ec596063af8cd273ebd9f67073e1208

Answer 4

pythonic one-liner:

$> python -c "import zlib,sys;print \
           repr(zlib.decompress(sys.stdin.read()))" < $IN

Answer 5

Looks like Mark Adler has us in mind and wrote an example of just how to do this with: http://www.zlib.net/zpipe.c

It compiles with nothing more than gcc -lz and the zlib headers installed. I copied the resulting binary to my /usr/local/bin/zpipe while working with git stuff.

Answer 6

Why don't you just use git's tools to access the data? This should be able to read any git object:

git show --pretty=raw <object SHA-1>