Files and directories have different levels of permissions which indicate who can read them, write to them, or even execute them.
- user - these permissions apply to the user who owns the file
- group - these permissions apply to the group that owns the file
- other - these apply to everyone else
- read - read the contents of the file
- write - write or modify the file/directory
- execute - execute the file or view the contents of the directory
Try this now:
BabyMac:~ jennapederson$ ls -l
total 8
-rw-rw-r-- 1 ubuntu ubuntu 699 Jul 1 13:37 README.md
-rw-r--r-- 1 ubuntu ubuntu 32 Sep 13 21:44 hello_world.sh
Our permissions are shown in the first column of characters in this format:
<special flag><user rwx><group rwx><other rwx>
Right now, the hello_world.sh file is not executable. We're going to fix that.
BabyMac:~ jennapederson$ ./hello_world.sh
bash: ./hello_world.sh: Permission denied
To make the hello_world.sh file executable, we will add execute permissions to the user.
Try this now:
BabyMac:~ jennapederson$ chmod u+x hello_world.sh
BabyMac:~ jennapederson$ ls -l
total 8
-rw-rw-r-- 1 ubuntu ubuntu 699 Jul 1 13:37 README.md
-rwxr--r-- 1 ubuntu ubuntu 32 Sep 13 21:44 hello_world.sh*
Note that the x bit has been added to the user level, indicated by u+x. If we wanted to remove group write, we would use g-w. If we wanted to remove read for other, we would use o-r.
- u, g, o for user, group, other respectively
-
- or - to add or remove
- r, w, x for read, write, execute respectively
The very first bit, the special flag, usually will indicate whether it is directory (d), regular file (-), or a link (l).
Try this now ex. 1:
BabyMac:~ jennapederson$ ./hello_world.sh
Hello World!
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