Compression decreases the size of data.

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62
votes
20answers
66k views

Compressing with RAR vs ZIP

A lot of people are compressing files with RAR, sending compressed files with RAR and so on. ZIP is more standard and works on all platforms. Windows users have ZIP included and Linux users have no ...
7
votes
5answers
4k views

How to open corrupted ZIP files?

How can I open (or repair) corrupted ZIP files on Windows? Is there a way to force 7-Zip to open them?
37
votes
8answers
40k views

What’s a good way to extract .rar files on the Mac? [closed]

Anything built-in? (E.g. command line tools.) Any well-regarded software? Update: I like The Unarchiver, but vote up your favourite, or add it as an answer if it isn’t there.
2
votes
5answers
8k views

Is there a way to use the built-in Windows file compression tool on the command line?

Instead of using Right-Click/Send To/Compress (Zipped) Folder. I am using Windows Server 2003 Enterprise Edition.
23
votes
2answers
24k views

What do the numbers 240 and 360 mean when downloading video? How can I tell which video is more compressed?

I have downloaded some computer science lectures from YouTube recently. There is usually more than one choice of file size and file format to download. I noticed that for the same video, the ...
18
votes
5answers
15k views

Compressing folders on a mac, without the .DS_Store

Is there anyway to get rid of the .DS_Store when compressing a folder on a mac? I work on a mac and send work to clients in zip format, but always get questioned on the .DS_Store folder inside them. ...
7
votes
6answers
1k views

Is there a free way to compress a PDF?

I have several PDFs that are quite large (one is 80+ MB). Is there a free way to compress that PDF to a smaller size?
10
votes
8answers
11k views

Why doesn't ZIP Compression compress anything?

A 398MB directory was only compressed to 393MB using 7Z and Normal ZIP compression. Is this normal? If so, why do people continue to use ZIP on Windows?
10
votes
9answers
22k views

Highest compression for files(for web transfer)?

I have seen some highly compressed files around, such as 700MB of data compressed to around 30-50MB. But how do you get such compressed files? I have tried using software like WinRAR and 7Zip but ...
1
vote
2answers
6k views

Compress a folder into multiple zip files

I'm on mac osx. 1. Is there any tool to compress a folder into multiple zip files ? 2. Is there any tool to split a compressed zip file into smaller zip files (to open individually later) ? thanks
4
votes
2answers
8k views

Convert old videos to have smaller sizes

I have some videos from a few years ago,with various formats, such as avi, mpg, wmv, rm, rmvb, .... Their sizes are huge(more than 500 MB, and sometimes > 1GB). Given there may likely be some ...
0
votes
5answers
4k views

How can I overwrite an existing file in 7zip?

I'm trying this: 7za.exe a "C:\Disc.7z" "C:\test" -v20000000b -m0=BCJ -bd But if I already have created the file C:\Disc.7z then 7zip don't compress nothing and sends me this output: System error: ...
30
votes
4answers
12k views

How does NTFS compression affect performance?

I've heard that NTFS compression can reduce performance due to extra CPU usage, but I've read reports that it may actually increase performance because of reduced disk reads. How exactly does NTFS ...
19
votes
2answers
12k views

Is zip's encryption really bad? [closed]

The standard advice for many years regarding compression and encryption has been that the encryption strength of zip is bad. Is this really the case in this day and age? I read this article about ...
3
votes
4answers
886 views

Compress pdf file? [duplicate]

I need to reduce the size or compress a PDF file. The PDF file is actually scanned images. Is there any way by which I can compress the file?
42
votes
4answers
42k views

How to specify level of compression when using tar -zcvf?

I gzip directories very often at work. What I normally do is tar -zcvf file.tar.gz /path/to/directory Is there a way to specify the compression level here? I want to use the best compression ...
15
votes
2answers
26k views

Is it possible to execute a file after extraction from a 7-Zip self-extracting archive (SFX) archive?

I'm try to make a compressed deploy-able application. Currently I'm taking a set of files that I've published from my IDE (Visual Studio 2008 - WPF published application) and compressing ...
22
votes
6answers
3k views

How can I evaluate the best choice of archive format for compressing files?

In general, I've observed the following: Linux-y files or tools use bzip2 or gzip for distributing archives Windows-y files or tools use ZIP for distributing archives Many people use 7-Zip for ...
8
votes
3answers
10k views

How to do “Files to store without compression” in 7-zip?

Is there any way to selectively prevent certain file types from compression in 7-zip, like in WinRAR? I'm trying to compress a huge folder (many gigabytes), and I don't want the already-compressed ...
8
votes
3answers
36k views

What settings to use when making 7zip files in order to get maximum compression when compressing PDFs?

What settings to use when making 7zip files in order to get maximum compression? I'm compressing PDF documents containing scanned images. I'm thinking about using LZMA2, but I don't know what to set ...
5
votes
8answers
4k views

Winrar-like archive utility for OS X

I've been a Mac user for about 1.5 years and so far enjoyed the experience. But one thing I miss from other operating systems is the lack of compression/decompression utilities that follow the ...
3
votes
4answers
2k views

Windows: Will compressing the hard drive partition speed up disk access? [duplicate]

Possible Duplicate: How does NTFS compression affect performance? In theory, on a reasonably fast PC, the processor is mostly idle during hard drive access. A compressed file takes up less ...
2
votes
2answers
665 views

Create multiple zip files that are not dependent on each other?

I want to compress a folder into multiple zip files of 50MB each but don't want them to be dependent on each other. When I use Winzip and use the split feature it creates one zip file and the others ...
2
votes
3answers
214 views

tar-ing / should I use -C / . or just /

tar cvf backup.tar -C / / # or tar cvf backup.tar / produces an archive like etc/ and gives warnings tar: Removing leading `/' from member names tar: Removing leading `/' from hard link ...
2
votes
3answers
11k views

How can I remove the password protection from a RAR archive? [duplicate]

I have a directory in which there are lots of password protected .RAR files/archives. The passwords of these individual archives are known. I want to remove the password protection from all of them ...
1
vote
4answers
986 views

Performance Decline after compressing entire C: drive

Hey guys, i recently tried to improve performance in my laptop by compressing files on the c: drive... however due to my own negligence i compressed the entire c: drive and not just the my documents ...
1
vote
4answers
30k views

Commandline to zip a file using WinRar

I looked for the answers in the list and did not find any matching. What is the commandline to zip a file using Winrar, and then move it to a particular folder?
0
votes
5answers
3k views

Does compressing files in XP slow things down?

I frequently run the Disk Cleanup tool and let it compress old files. However, one of the directories it compressed, full of small icon images, is terribly slow. Is this a result of the compression or ...
10
votes
6answers
17k views

How do I uncompress vmlinuz to vmlinux?

I have already tried uncompress, gzip, and all other solutions that come up as google results and these have not worked for me. To get just the image search for the GZ signature - 1f 8b 08 00. ...
72
votes
11answers
3k views

Can zipping a file break it?

I just asked someone to send me a zipped psd file. They declined, citing that zipping a file can break the fonts. I assumed zipping a file is perfectly reversible, hence why it is commonly used. I ...
35
votes
5answers
21k views

Pros and cons of bzip vs gzip?

I've known gzip for years, recently I saw bzip being used at work. Are they basically equivalent, or are there significant pros and cons to one of them over the other?
34
votes
5answers
3k views

Why is a 7zipped file larger than the raw file? [duplicate]

Possible Duplicate: Why doesn't ZIP Compression compress anything? I tried 7zipping an .exe file but it actually became larger. Is this the expected result?
7
votes
6answers
13k views

How can I achieve the best, standard ZIP compression?

I don't care how long it takes to compress, all I want to achieve is two things: The absolute best possible compression ratio Compatibility with standard readers, such as Windows and WinZip So ...
12
votes
4answers
2k views

Why is a FLAC encoded from a decoded MP3 bigger than the MP3?

To be more precise than in the title, suppose I have a MP3 file that is 320 kbps. If I decompress it, then logically, all the data except for roughly 320 kilobits out of each second of audio should be ...
6
votes
1answer
2k views

Compressing a file in place - does “gzip -c file | dd of=file” really work?

In the question How can I compress a file on Linux in-place, without using additional disk space?, one answer proposes to simply use gzip -c file | dd of=file I tried it (on Debian Linux), and it ...
8
votes
1answer
5k views

How does 'dictionary size' affect compression?

I know that higher size may lead to better compression ratio and vice verca. But is there a way I can decide better?.. since there are so many choices So far I've noticed dictionary size ≈ file ...
7
votes
4answers
2k views

Is there a compression or archiver program for Windows that also does deduplication?

I'm looking for an archiver program that can perform deduplication (dedupe) on the files being archived. Upon unpacking the archive, the software would put back any files it removed during the ...
5
votes
3answers
4k views

Do encrypted compression containers like ZIP and 7-Zip compress or encrypt first?

The discussion of "compress and then encrypt, or vice-versa" led me to ponder the following question: many compression containers, like ZIP, 7z, and rar support encrypting these containers. For ...
0
votes
2answers
452 views

What is the difference in various commands for compressing files in linux?

What are the commands for compressing files in linux and what are the difference between them? (for example: tar, gzip, rar). I'm working on Linux Mint 11 and doing a script for compressing files. I ...
8
votes
4answers
4k views

How can I compress a file on Linux in-place, without using additional disk space?

I've got a 100GB drive that has a 95GB file. I need to free up some space on the drive (and right now transferring the file off the drive is not an option). The file would compress well with gzip or ...
3
votes
4answers
591 views

How to avoid compressing compressed files

Most compression programs compress all files by default. But when archiving a folder containing already compressed files, there is no need to compress them a second time, such as archives, packed ...
2
votes
2answers
1k views

Creating .xz with 7-Zip, claims insufficient memory (not true)

In WinXP 32bit with a Core i5 (dual core) and 4GB RAM, I'm trying to create an .xz archive from a 266MB log file using 7-Zip (GUI) on the "ultra" compression level (method: LZMA2, dictionary size: ...
4
votes
3answers
3k views

Recursively unzip files where they reside, then delete the archives

I goofed up a setting on the backup software I use. Normally I would have the files from a network share get loaded into a spare drive, compressed into zip folders, then sent off to the offsite hub. ...
3
votes
2answers
2k views

zip: Argument list too long (80.000 files in overall)

I need to compress 80.000 files into multiple zip files. This is the command I use: zip -s 200M photos_test/* However I get the following error: -bash: /usr/bin/zip: Argument list too long What ...
2
votes
2answers
455 views

What does the number after 7-zip's -m switch mean?

7-zip has a command line switch to set the compression method, -m followed by a number, e.g. -m0=LZMA. What does the number (0 in the example) mean? Different numbers produce slightly different ...
2
votes
3answers
2k views

Why does a zip file appear larger than the source file especially when it is text?

I have a text file that is 19 bytes in size and having compressed the file using zip and 7zip, it appears to be larger. I had a read of the question on Why is a 7zipped file larger than the raw file? ...
2
votes
1answer
238 views

Why is the NTFS compression setting ignored by some applications?

I use NTFS compression on some folders, I understand the pros and cons of this, but for my use case it is preferred. I have noticed some odd behavior for many years. Some applications do not "honor" ...
2
votes
1answer
4k views

How to compress .pdfs in word 2007?

I am trying to send my cover letter and resume away but apparently it is too big to send through craigs list(my computer says the total size is 500kb) as it has a 600kb limit(so small should be at ...
2
votes
4answers
2k views

Good and free unzipping software for Mac? [closed]

What is a good and free unzipping software for Mac? Good as in...supporting different types of compressed files and can unlock password protected ones. The built-in one on Mac doesn't do a good job ...
1
vote
2answers
154 views

How can I search for files that are either compressed or uncompressed in Windows Explorer?

I know that Windows explorer can colorize the NTFS compression state of a file, in both the regular and search views. How can I specifically filter/search for files that are compressed or ...