File Compression

bzip2(.bz2):

Burrows-Wheeler block sorting text compression algorithm, and Huffman coding è il più efficiente in termini di spazio utilizzato

bzip2 mydata.doc
bzip2 *.jpg
# interesting flags:
   -d --decompress     force decompression
   -z --compress       force compression
   -k --keep           keep (don't delete) input files
   -f --force          overwrite existing output files
   -q --quiet          suppress noncritical error messages
   -v --verbose        be verbose (a 2nd -v gives more)
   -s --small          use less memory (at most 2500k)
   -1 .. -9            set block size to 100k .. 900k
   --fast              alias for -1
   --best              alias for -9

decompressione:

bzip2 -d mydata.doc.bz2
gunzip mydata.doc.bz2

gzip(.gz): Lempel-Ziv coding (LZ77)

gzip mydata.doc
gzip *.jpg

decompressione:

gzip -d mydata.doc.gz
gunzip mydata.doc.gz

comprimere un file e contare i bytes

uglifyjs yourlib.js | gzip -9f | wc -c

zip(.zip):

molto portabile su windows.

zip -r filename.zip files
zip -r9  filename.zip folder
zip mydata.zip mydata.doc
zip data.zip *.doc

decompressione:

unzip filename.zip
unzip data.zip resume.doc

tar (.tgz)

# create zipped file
tar -cvzf filename.tar.gz files/directories
#extract
tar -xvf foo.tar
 
#-z: use gzip compress
#-j: use bzip2 compress
tar -zcvf data.tgz *.doc
tar -zcvf pics.tar.gz *.jpg *.png
tar -jcvf data.tbz2 *.doc

decompressione:

tar -zxvf data.tgz
tar -zxvf pics.tar.gz *.jpg
tar -jxvf data.tbz2

file listing

gzip -l mydata.doc.gz
unzip -l mydata.zip
tar -ztvf {.tar.gz}
tar -jtvf data.tbz2

quale metodo di compressione?

Best compression: size

  1. 7z 493
  2. rar 523
  3. bz2 592
  4. gz 614
  5. Z 614
  6. zip 614