之前有寫利用md5方式來做差異備份，但是這種md5方式來寫存在以下問題：

•md5sum獲取有些軟連接的MD5值存在問題
•不支持對空目錄進行備份，因為md5sum無法獲取空目錄的md5值
•權限的修改md5sum無法判斷

解決方案：

利用文件的mtime ctime

mtime（Modified time）是在寫入文件時隨文件內容的更改而更改的
ctime（Create time）是在寫入文件、更改所有者、權限或鏈接設置時隨Inode的內容更改而更改的
廢話不多說直接上代碼：

#!/usr/bin/env pythonimport time,os,sys,cPicklefileInfo = {}def logger(time,fileName,status,fileNum):  f = open('backup.log','a')  f.write("%s/t%s/t%s/t/t%s/n" % (time,fileName,status,fileNum))def tar(sDir,dDir,fileNum):  command = "tar zcf %s %s >/dev/null 2>&1" % (dDir + ".tar.gz",sDir)  if os.system(command) == 0:    logger(time.strftime('%F %X'),dDir + ".tar.gz",'success',fileNum)  else:    logger(time.strftime('%F %X'),dDir + ".tar.gz",'failed',fileNum)def fullBak(path):  fileNum = 0  for root,dirs,files in os.walk(path):    for name in files:      file = os.path.join(root, name)      mtime = os.path.getmtime(file)      ctime = os.path.getctime(file)      fileInfo[file] = (mtime,ctime)      fileNum += 1  f = open(P,'w')  cPickle.dump(fileInfo,f)  f.close()  tar(S,D,fileNum)def diffBak(path):  for root,dirs,files in os.walk(path):    for name in files:      file = os.path.join(root,name)      mtime = os.path.getmtime(file)      ctime = os.path.getctime(file)      fileInfo[file] = (mtime,ctime)  if os.path.isfile(P) == 0:    f = open(P,'w')    f.close()  if os.stat(P).st_size == 0:    f = open(P,'w')    cPickle.dump(fileInfo,f)    fileNum = len(fileInfo.keys())    f.close()    print fileNum    tar(S,D,fileNum)  else:    f = open(P)    old_fileInfo = cPickle.load(f)    f.close()    difference = dict(set(fileInfo.items())^set(old_fileInfo.items()))    fileNum = len(difference)    print fileNum    difference_file = ' '.join(difference.keys())    print difference_file    tar(difference_file,D,fileNum)    f = open(P,'w')    cPickle.dump(fileInfo,f)    f.close()def Usage():  print '''    Syntax: python file_bakcup.py pickle_file model source_dir filename_bk      model: 1:Full backup 2:Differential backup    example: python file_backup.py fileinfo.pk 2 /etc etc_$(date +%F)      explain: Automatically add '.tar.gz' suffix  '''  sys.exit()if len(sys.argv) != 5:  Usage()P = sys.argv[1]M = int(sys.argv[2])S = sys.argv[3]D = sys.argv[4]if M == 1:  fullBak(S)elif M == 2:  diffBak(S)else:  print "/033[;31mDoes not support this mode/033[0m"  Usage()

測試：

$ python file_backup.py data.pk 1 data data_$(date +%F) #全備份$ > data/www.jb51.net #測試創建文件，修改文件權限$ chmod 777 data/py/eshop_bk/data.db$ python file_backup.py data.pk 2 data data_$(date +%F)_1 #備份改變的文件2data/py/eshop_bk/data.db data/www.jb51.net