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Operating Systems Linux Red Hat Compression ratios of .tbz file Post 302554790 by pludi on Tuesday 13th of September 2011 04:59:38 AM
Old 09-13-2011
In short: no.
tar doesn't compress anything, it's just an archiver, meaning it combines a list of files (including meta information like access times, permissions, ...) into one larger file. As a bonus it supports passing this file stream through a compression utility like gzip or bzip2. These 2 commands are completely equal, and the resulting files usually even have the same checksum:
Code:
# tar -cf - directory | bzip2 -c > archive.tbz
# tar -cjf archive.tbz directory

One way to get the ratio would be by getting the sizes of the original and the compressed file with du, and feeding it to bc:
Code:
orig=$( du -k directory )
comp=$( du -k archive.tbz )
ratio=$( echo "scale=5; $comp/$orig*100" | bc )

 

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7z(1)							      General Commands Manual							     7z(1)

NAME
7z - A file archiver with highest compression ratio SYNOPSIS
7z [adeltux] [-] [SWITCH] <ARCHIVE_NAME> <ARGUMENTS>... DESCRIPTION
7-Zip is a file archiver with the highest compression ratio. The program supports 7z (that implements LZMA compression algorithm), LZMA2, XZ, ZIP, Zip64, CAB, RAR (if the non-free p7zip-rar package is installed), ARJ, GZIP, BZIP2, TAR, CPIO, RPM, ISO, most filesystem images and DEB formats. Compression ratio in the new 7z format is 30-50% better than ratio in ZIP format. 7z uses plugins to handle archives. FUNCTION LETTERS
a Add d Delete e Extract l List t Test u Update x eXtract with full paths SWITCHES
-ai[r[-|0]]{@listfile|!wildcard} Include archives -ax[r[-|0]]{@listfile|!wildcard} eXclude archives -bd Disable percentage indicator -i[r[-|0]]{@listfile|!wildcard} Include filenames -l don't store symlinks; store the files/directories they point to (CAUTION : the scanning stage can never end because of recursive symlinks like 'ln -s .. ldir') -m{Parameters} Set Compression Method (see /usr/share/doc/p7zip-full/DOCS/MANUAL/switches/method.htm for a list of methods) -mhe=on|off 7z format only : enables or disables archive header encryption (Default : off) -o{Directory} Set Output directory -p{Password} Set Password -r[-|0] Recurse subdirectories (CAUTION: this flag does not do what you think, avoid using it) -sfx[{name}] Create SFX archive -si Read data from StdIn (eg: tar cf - directory | 7z a -si directory.tar.7z) -so Write data to StdOut (eg: % echo foo | 7z a dummy -tgzip -si -so > /dev/null) -slt Sets technical mode for l (list) command -t{Type} Type of archive (7z, zip, gzip, bzip2 or tar. 7z format is default) -v{Size}[b|k|m|g] Create volumes -u[-][p#][q#][r#][x#][y#][z#][!newArchiveName] Update options -w[path] Set Working directory -x[r[-|0]]]{@listfile|!wildcard} Exclude filenames -y Assume Yes on all queries DIAGNOSTICS
7-Zip returns the following exit codes: 0 Normal (no errors or warnings detected) 1 Warning (Non fatal error(s)). For example, some files cannot be read during compressing. So they were not compressed 2 Fatal error 7 Bad command line parameters 8 Not enough memory for operation 255 User stopped the process with control-C (or similar) Backup and limitations DO NOT USE the 7-zip format for backup purpose on Linux/Unix because : - 7-zip does not store the owner/group of the file. On Linux/Unix, in order to backup directories you must use tar : - to backup a directory : tar cf - directory | 7za a -si directory.tar.7z - to restore your backup : 7za x -so directory.tar.7z | tar xf - If you want to send files and directories (not the owner of file) to others Unix/MacOS/Windows users, you can use the 7-zip format. example : 7za a directory.7z directory Do not use "-r" because this flag does not do what you think. Do not use directory/* because of ".*" files (example : "directory/*" does not match "directory/.profile") EXAMPLE 1 7z a -t7z -m0=lzma -mx=9 -mfb=64 -md=32m -ms=on archive.7z dir1 adds all files from directory "dir1" to archive archive.7z using "ultra settings" -t7z 7z archive -m0=lzma lzma method -mx=9 level of compression = 9 (Ultra) -mfb=64 number of fast bytes for LZMA = 64 -md=32m dictionary size = 32 megabytes -ms=on solid archive = on EXAMPLE 2 7z a -sfx archive.exe dir1 add all files from directory "dir1" to SFX archive archive.exe (Remark : SFX archive MUST end with ".exe") EXAMPLE 3 7z a -mhe=on -pmy_password archive.7z a_directory add all files from directory "a_directory" to the archive "archive.7z" (with data and header archive encryption on) SEE ALSO
7za(1), 7zr(1), bzip2(1), gzip(1), zip(1) HTML Documentation /usr/share/doc/p7zip-full/DOCS/MANUAL/index.htm AUTHOR
Written for Debian by Mohammed Adnene Trojette. Mohammed Adnene Trojette September 1 2006 7z(1)
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