第 4 章 Example

如果 logfile 值已經存在側不會覆蓋

$ logfile=/var/log/test.log

$ echo $logfile
/var/log/test.log

$ logfile=${logfile:-/tmp/test.log}

$ echo $logfile
/var/log/test.log
    	

如果變數為空才能設置

$ unset logfile
$ logfile=${logfile:-/tmp/test.log}
$ echo $logfile
/tmp/test.log    	
    	

$ unset logfile