crontab中下面的腳本不能
0 1 * * * (cd /u01/prod; rsync -avz app 192.168.0.192:/u01/prod/) &>/home/applprod/backuplog/rsync_`date +%Y%m%d_%H%M%S`.log
執行的時候，/var/log/messages日誌中顯示：
Sep 22 22:50:01 ebsapp CROND[13389]: (applprod) CMD ((cd /u01/prod; rsync -avz app 192.168.0.192:/u01/prod/) &>/home/applprod/backuplog/rsync_`date +)
好像是指令被截斷的樣子。
於是我把要執行的指令都封裝到一個腳本中，放到crontab中執行。
但是稍後查看crontab的manpage時發現，%在crontab中有特殊意義：
The "sixth" field (the rest of the line) specifies the command to be run. The entire command portion of the line, up to a new- line or % character, will be executed by /bin/sh or by the shell specified in the SHELL variable of the cronfile. Percent-signs (%) in the command, unless escaped with backslash (\), will be changed into newline characters, and all data after the first % will be sent to the command as standard input.
到這裡問題已經清楚了，並不是crontab指令被截斷，而是被理解成另外的意義了，解決的方法也有了，就是將%進行轉義，修改之後的腳本變成了：
03 23 * * * (cd /u01/prod; rsync -avz app 192.168.0.192:/u01/prod/) &>/home/applprod/backuplog/rsync_`date +\%Y\%m\%d_\%H\%M\%S`.log