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檔案壓縮

檔案壓縮. 壓縮是經由清除重覆的部分 , 而降低檔案所佔的空間，和降低網路檔案傳輸所需的時間 兩種基本的壓縮的方式 lossy lossless. compress Lempel-Ziv 壓縮技術 原檔名 .Z 看內容 zcat 刪除掉舊的檔案 解壓縮 uncompress 在二進位檔有較佳效果. 顯示過程 compress – v file1 壓縮 dir1 目錄 compress –r dir1 解壓 compress – d file1.Z 將檔案壓縮後另存新檔 ( 不可用於目錄 )

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檔案壓縮

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  1. 檔案壓縮 • 壓縮是經由清除重覆的部分,而降低檔案所佔的空間，和降低網路檔案傳輸所需的時間 • 兩種基本的壓縮的方式 • lossy • lossless

  2. compress Lempel-Ziv壓縮技術 原檔名.Z 看內容zcat 刪除掉舊的檔案 解壓縮uncompress 在二進位檔有較佳效果 顯示過程 compress –v file1 壓縮dir1目錄 compress –r dir1 解壓 compress –d file1.Z 將檔案壓縮後另存新檔(不可用於目錄) compress –c file1 > file1.Z 節省空間

  3. c (create),建立 v(verbose),列印 t(table of content),表列 x(extract),抽取 f(file) Backup to tape tar cvf /dve/rmt0 /usr/bin Restore from tape tar xvf /dev/rmt0 Tar收集檔案

  4. Tar收集檔案 • Backup to a file tar -cvf letters.tra *.ltr • View tar file tar –tvf letters.tar • Extra one file tar -xvf letters.tar sam1.ltr • Extra files tar -xvf letters.tar

  5. 收集整個目錄 cd fromdir; tar cf - . | (cd todir; tar xpf -) • The tar command uses the next argument as the name of the archive instead of /dev/rmtnh. • If the name of the file is - (dash), tar writes to standard output or reads from standard input, whichever is appropriate. • Thus, tar can be used as the head or tail of a filter chain. tar cvf - . |(cd ../../users/gordon;tar xvf -)

  6. cd fromdir; tar cf - . | (cd todir; tar xpf -) standard I/O Preserve files to therir original modes

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