Dr Olga is a motivational speaker, and a writer. Dr Olga has earned her PhD at UCLA in Globalization Studies and brings new innovative methods of informing the 4 dimensional education. Her pedagogical skills are unique.
Download books and articles by Dr Olga lazin here: http://www.olgalazin.com
Shop Dr Olga Essential Oils here; https://dr-olga-essential-oils.myshopify.com
Many Thanks for efficiency. How can I add to seller Topics on the forum? How do I start a Topic, please? Thanks
Is there a Windows interface for gzip?
PowerArchiver 6.1, 7-zip and Winzip include the gzip compression code and can decompress .gz and tar.gz files. Win-GZ can compress and decompress files in gzip format. Please note that gzip, 7-zip, PowerArchiver 6.1 and Win-GZ are freeware but you must register Winzip and PowerArchiver > 6.1 if you use them regularly.
Can I adapt the gzip sources to perform in-memory compression?
If you use the commands described above to extract a tar.gz file, gzip sometimes emits a Broken pipe error message. This can safely be ignored if tar extracted all files without any other error message.
The reason for this error message is that tar stops reading at the logical end of the tar file (a block of zeroes) which is not always the same as its physical end. gzip then is no longer able to write the rest of the tarfile into the pipe which has been closed.
This problem occurs only with some shells, mainly bash. These shells report the SIGPIPE signal to the user, but most others (such as tcsh) silently ignore the pipe error.
You can easily reproduce the same error message with programs other than gzip and tar, for example:
cat /dev/zero | dd bs=1 count=1
gzip complains with trailing garbage ignored
Some tar.gz files are padded with zeroes to have a size which is a multiple of a certain block size. This occurs in particular when the compressed tar file is on a device such as a magnetic tape. When such files are extracted with a command such as
gunzip < file.tar.gz | tar xvf -
gtar xvzf /dev/rmt/0
gunzip decompresses correctly the tar.gz file, then attempts to decompress the rest of the input which consists of zeroes. Since those zeroes are not in gzip format, gzip ignores them. The tar extract command still works correctly, since gzip has sent through the pipe all the data that tar needs.
You can avoid this harmless warning by using the -q option of gzip, as in:
gunzip -q < file.tar.gz | tar xvf -
GZIP=-q gtar xvzf /dev/rmt/0 # for bash, ksh, sh ...
(setenv GZIP -q; gtar xvzf /dev/rmt/0) # for csh, tcsh, ...
My hard disk has bad sectors. Can I still recover my .gz files?
You know this already, but let me repeat it again: there is no substitute for backups. If you use gzip for important backups, you must test the backups before deleting the original files. To test a tar.gz file, do:
for GNU tar: tar tvfz file.tar.gz
for any tar: gunzip < file.tar.gz | tar tvf -
If you transfer the tar.gz file to another machine, test the destination file (after the file transfer), not the source file. This will detect bad file transfers. If you are not using tar, do at least gzip -tv file.gz to test important files. Once the damage is made, it is somewhere between extremely difficult and impossible to recover damaged .gz files. If your data is so valuable that you are willing to spend a lot of time to recover part of it, read this.
Can gzip handle files of more than 4 gigabytes?
Yes, but you need this patch to the gzip 1.2.4 sources, or use the beta version 1.3.x. See section executables to download binaries with the patch already included.
Files already compressed without the patch are correct; the patch is useful only for decompression. Decompression with zcat outputs the correct data plus an error message length error that you can ignore for a single file. For example you can decompress with
gunzip < file.gz > file
zcat on multiple files will stop at the first error so use the patch to avoid any problem.
To get a corrected binary, save the file 4g-patch.tar in the directory containing the gzip sources, then do:
tar xvf 4g-patch.tar
For some systems (Solaris 2.6, AIX), you may get the error message "Value too large for defined data type". A complete source tree fixing this problem is available here, thanks to Paul Eggert. For AIX, compile add "-D_POSIX_SOURCE -D_LARGE_FILES -D_LARGE_FILE_API" to the compilation flags.
What about patents?
gzip was developed as a replacement for compress because of the UNISYS and IBM patents covering the LZW algorithm used by compress.
I have probably spent more time studying data compression patents than actually implementing data compression algorithms. I maintain a list of several hundred patents on lossless data compression algorithms, and I made sure that gzip isn't covered by any of them. In particular, the --fast option of gzip is not as fast it could, precisely to avoid a patented technique.
The first version of the compression algorithm used by gzip appeared in zip 0.9, publicly released on July 11th 1991. So any patent granted after July 11th 1992 cannot threaten gzip because of the prior art, and I have checked all patents granted before this date.
During my search, I found two interesting patents on a process which is mathematically impossible: compression of random data. This is somewhat equivalent to patents on perpetual motion machines. Check herefor a short analysis of these two patents.
gzip handles correctly dates within or after year 2000. More information about GNU software and year 2000 can be found here.
I get a compilation error about utimbuf
On systems which declare utimbuf in unistd.h instead of utime.h or sys/utime.h (such as AIX), use:
I can't compile gzip on Solaris
You need a compiler to compile gzip and you need gzip to get gcc. To get out of this loop, install first the gzip binary for Solaris (Sparc or i386). See also here for beta versions.
Does gzip support encryption?
No. Simple encryption algorithms such as that of PKZIP can be broken. And adding strong encryption such as that of PGP to gzip would not make much sense because that would duplicate the functionality of those encryption programs. PGP already incorporates the gzip compression code, so use PGP if you need compression plus strong encryption.
If you are satisfied with weak encryption, you can use zip.
Can gzip compress several files into a single archive?
Not directly. You can first create a tar file then compress it:
for GNU tar: gtar cvzf file.tar.gz filenames
for any tar: tar cvf - filenames | gzip > file.tar.gz
Alternatively, you can use zip, PowerArchiver 6.1, 7-zip or Winzip. The zip format allows random access to any file in the archive, but the tar.gz format usually gives a better compression ratio.
The AOL web page for AOL Instant Messenger incorrectly detects the WebTV browser as a Unix browser. Therefore WebTV users are shown by mistake the page for TiK, which cannot work for WebTV. So please do not email me about AOL Instant Messenger or WebTV. The instructions telling you to dowload gzip cannot work for WebTV.
In any case, there is no way to use AOL Instant Messenger on WebTV. Emailing me about this will not help in any way, I am not related to either WebTV or AOL. The correct contact for WebTV is here. Once again, the web page which led you here contains an error, you must not follow the instructions meant for Unix users only. Thank you for your understanding.
The home page of gzip's author Jean-loup Gailly The home page of gzip's co-author Mark Adler The data compression library, also written by Jean-loup and Mark.