允许列出目录下面的文件，即允许读取目录的内容。没有读权限，ls目录会失败。
$ ls 134
ls: cannot open directory '134': Permission denied
但是可以读取目录中子文件的内容：
$ cat 134/a
允许修改目录的内容（如新建、删除子文件），没有写权限，在目录下创建文件会失败：
$ touch 134/c
touch: cannot touch '134/c': Permission denied
允许访问目录中的文件。注意：写权限是针对目录下条目增删，而执行权限，是针对目录下的文件本身。
没有执行执行权限，则不能读、写目录下的子文件内容，也不能访问和修改子文件的属性等。
$ echo 123 > 134/a
$ chmod -x 134/
$ echo 123 > 134/a
-bash: 134/a: Permission denied
如上，之前有wx权限，所以可以新建条目（w），可以写入内容（x）。去掉x权限后，不能再修改文件内容。
没有执行权限
ls -l会失败，但是\ls会成功，前者会访问文件的属性。ls默认是alias ls='ls --color=auto'，也会失败。
https://www.redhat.com/sysadmin/linux-file-permissions-explained
This permission is very different on directories compared to files. Essentially, you can think of it as providing access to the directory. Having execute permission on a directory authorizes you to look at extended information on files in the directory (using ls -l, for instance) but also allows you to change your working directory (using cd) or pass through this directory on your way to a subdirectory underneath.
Lacking execute permission on a directory can limit the other permissions in interesting ways. For example, how can you add a new file to a directory (by leveraging the write permission) if you can't access the directory's metadata to store the information for a new, additional file? You cannot. It is for this reason that directory-type files generally