find命令问题

songyc_2015

请教大神一个问题：

需求：在当前目录下（不查询databak子目录），查找符合"*20150408*"的文件

在当前目录下：
$ls -F
20150408/     20150408.tar      databak/

$find ./ \( -name "databak" -prune \) -o -name "*20150408*" -type f -print
./20150408.tar

$find ./ \( -name "databak" -prune \) -o -name "*20150408*" -type f
./20150408.tar
./databak

测试系统：IBM AIX6.1

问题：
1.为什么第2条find少了-print选项，结果会多出一个"./databak"？
2.-print是find命令默认选项吗？

songyc_2015

知道答案了，因为：

The  expression  is  made  up of options (which affect overall operation rather than the processing of a specific file, and always return true),
tests (which return a true or false value), and actions (which have side effects and return a true or false value), all separated by  operators.
-and is assumed where the operator is omitted.

If the expression contains no actions other than -prune, -print is performed on all files for which the expression is true.
所以：一下命令是等价的：
find ./ \( -name "databak" -prune \) -o -name "*20150408*" -type f
find ./ \( \( -name "databak" -a -prune \) -o \( -name '*20150408*' -a -type f \) \) -a -print
find ./ \( -name "databak" -prune -a -print \) -o -name "*20150408*" -type f -a -print

因此结果多了一个"./databak"