Error: 'zlib' is an invalid command

Question

How can I run this command in OSX?

dd if=mybackup.ab bs=24 skip=1|openssl zlib -d > mybackup.tar

When I run this I get the following errors

$ dd if=mybackup.ab bs=24 skip=1|openssl zlib -d > mybackup.tar dd: mybackup.ab: No such file or directory openssl:Error: 'zlib' is an invalid command.  Standard commands asn1parse      ca             ciphers        crl            crl2pkcs7       dgst           dh             dhparam        dsa            dsaparam        ec             ecparam        enc            engine         errstr          gendh          gendsa         genrsa         nseq           ocsp            passwd         pkcs12         pkcs7          pkcs8          prime           rand           req            rsa            rsautl         s_client        s_server       s_time         sess_id        smime          speed           spkac          verify         version        x509             Message Digest commands (see the `dgst' command for more details) md2            md4            md5            mdc2           rmd160          sha            sha1             Cipher commands (see the `enc' command for more details) aes-128-cbc    aes-128-ecb    aes-192-cbc    aes-192-ecb    aes-256-cbc     aes-256-ecb    base64         bf             bf-cbc         bf-cfb          bf-ecb         bf-ofb         cast           cast-cbc       cast5-cbc       cast5-cfb      cast5-ecb      cast5-ofb      des            des-cbc         des-cfb        des-ecb        des-ede        des-ede-cbc    des-ede-cfb     des-ede-ofb    des-ede3       des-ede3-cbc   des-ede3-cfb   des-ede3-ofb    des-ofb        des3           desx           rc2            rc2-40-cbc      rc2-64-cbc     rc2-cbc        rc2-cfb        rc2-ecb        rc2-ofb         rc4            rc4-40         rc5            rc5-cbc        rc5-cfb         rc5-ecb        rc5-ofb        seed           seed-cbc       seed-cfb        seed-ecb       seed-ofb      

Answer 1

Openssl on mac is compiled without zlib support. Alternative method described in this article works on my Yosemite:

dd if=backup.ab bs=1 skip=24 | python -c "import zlib,sys;sys.stdout.write(zlib.decompress(sys.stdin.read()))" | tar -xvf - 

Optionaly, if you just want to convert it into tar archive:

dd if=backup.ab bs=1 skip=24 | python -c "import zlib,sys;sys.stdout.write(zlib.decompress(sys.stdin.read()))" > backup.tar 

It skips first 24 bytes of Android header and then uncompresses zlib data.