File access permissions on UNIX-like systems such as Linux
About access permissions for UNIX-like systems such as Linux
I researched file access permissions on UNIX-like systems such as Linux and am leaving a note here. Please tell me if anything is incorrect.
ls -lをMacOSでやると、こういうのが出てくる。
❯ ls -al
total 1632
drwxr-xr-x@ 206 my-name staff 6592 Nov 5 16:17 .
drwx------@ 785 my-name staff 25120 Nov 5 15:50 ..
-rw-r--r--@ 1 my-name staff 12292 Nov 5 16:18 .DS_Store
drwxr-xr-x@ 80 my-name staff 2560 Nov 5 16:16 001-039
-rw-rw-r--@ 1 my-name staff 32 Nov 5 16:00 001.csv
-rw-rw-r--@ 1 my-name staff 14 May 11 2022 001.txt
...It's a command to list files, but what's that -rw-rw-r--@ on the left?
Permission notation on UNIX-like systems
According to what I found, UNIX-like OSes express permissions in this way. The leading - and the following three groups represent permissions for user, group, and others.
Breaking down -rw-rw-r--@ gives - | rw- | rw- | r-- | @.
- The first character is either
-ord;dindicates the entry is a directory. - The subsequent groups of three characters indicate permissions (described below).
- The three-character group repeats three times. The first is the owning user, the next is the owning group, and the last is other users.
- In the example
-rw-rw-r--@ 1 my-name staff 14 May 11 2022 001.txt, my-name is the owner, and staff is the owning group. - If it's
rwxrwxrwx, everything is permitted.
- The trailing
@indicates extended attributes are present on certain OSes like macOS. (On some OSes it might be+?)- The rwxrwxrwx settings alone aren't always sufficient, so macOS adds extra information.
Explanation of permission types
Their meanings are as follows:
| Character | Meaning |
|---|---|
- |
Not allowed |
r |
Read - read permission |
w |
Write - write permission |
x |
eXecute - execute permission |
If read and write are allowed but execute is not, it would look like rw-.
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