关于PATH变量的疑问

winway1988

$PATH
Path to binaries, usually /usr/bin/, /usr/X11R6/bin/, /usr/local/bin, etc.
When given a command, the shell automatically does a hash table search on the directories listed in
the path for the executable. The path is stored in the environmental variable, $PATH, a list of
directories, separated by colons. Normally, the system stores the $PATH definition in
/etc/profile and/or ~/.bashrc (see Appendix G).
bash$ echo $PATH
/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin:/sbin:/usr/sbin
PATH=${PATH}:/opt/bin appends the /opt/bin directory to the current path. In a script, it
may be expedient to temporarily add a directory to the path in this way. When the script exits, this
restores the original $PATH (a child process, such as a script, may not change the environment of the
parent process, the shell).
The current "working directory", ./, is usually omitted from the $PATH as a security
measure.

这是ABS里关于PATH变量的解释。
其中提到

When given a command, the shell automatically does a hash table search on the directories listed in
the path for the executable.

这里的"hash table search"指的是什么？
还有

The current "working directory", ./, is usually omitted from the $PATH as a security
measure.

这句也没理解安全在哪？
请大家指点，谢谢。

ontherd

google

waker

这里的"hash table search"指的是什么？是用内存存放的表，避免多次去外存找同样的文件

如果别人在你的某个目录里放个文件ls，功能是自动播放东京热，你在这个目录下面ls就有可能被老板炒了或被老板娘包了，如果./不在PATH里就相对“安全”一点儿

winway1988

回复 3# waker


    谢谢waker

xrzs1986

回复 3# waker


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