who can explain this test condition: [ -h "$element" -a ! -e

littlebat

This test condition is come from Example 7-4. Testing for broken links
in http://www.tldp.org/LDP/abs/html/fto.html
I know the meaning of "-h", "-a", "!" and "-e", but I don't know the
meaning of the test condition of putting them together.

This is my understanding:
-h "$element" : test if "$element" is a symbolic link;
! -e "$element" : test if "$element" isn't exist;

But, I can't understand this entire test condition, who can give a
explain? thanks.

kiron

http://www.linuxsir.cn/main/doc/ ... comparison-ops.html

yongjian

Post by littlebat
This test condition is come from Example 7-4. Testing for broken links
in http://www.tldp.org/LDP/abs/html/fto.html
I know the meaning of "-h", "-a", "!" and "-e", but I don't know the
meaning of the test condition of putting them together.

This is my understanding:
-h "$element" : test if "$element" is a symbolic link;
! -e "$element" : test if "$element" isn't exist;

But, I can't understand this entire test condition, who can give a
explain? thanks.

This is to test if a symlink is pointing to a non-existing file. You can create a file and then symlink it. Test with this statement and then remove the file and then test again.

Iambitious

的确是这样，但是我比较疑惑，为什么会是如此效果阿，按道理来说
symbol link本身就是一个文件阿，-e "$element"应该测试的是symbol link文件本身阿？

shizi4838

"symbol link本身就是一个文件阿",我不晓得这种说法对不对,但测试"symbol link文件本身"存在与否是没有意思的,关键是指向的链接文件存在不存在.

yongjian

Post by Iambitious
的确是这样，但是我比较疑惑，为什么会是如此效果阿，按道理来说
symbol link本身就是一个文件阿，-e "$element"应该测试的是symbol link文件本身阿？

symlink is actually a pointer pointing to the path of the target file, all filesystem functions will act on the real file directly and transparently.

Iambitious

哦，我明白了，看来是我对symbol link理解的不对了。谢谢了！

littlebat

谢谢各位啦，虽然对符号链接和它链接的真实文件的关系还是不大明白。
我可以暂时把[ -e "$element" ] 理解为：测试一个链接符号（文件）存在与否就是测试它所代表的真实文件是否存在；也没有一个东西用来专门测试链接符号是否存在。

我对yongjian的

               
symlink is actually a pointer pointing to the path
of the target file, all filesystem functions will
act on the real file directly and transparently.

还有点异议，像作用在符号链接上的rm, mv等命令就是对链接符号操作的，而像vi等命令才是对真实文件操作的。

寂寞烈火

rm,mv对文件的inode操作