In Bash, file permissions determine who can read, write, and execute a file. Each file in a Unix-like system has associated permissions that define what actions can be performed on the file by different users or user groups. The permissions are represented by a combination of letters and symbols. Here’s a breakdown of the file permissions and their meanings:
- r (read): Users with read permission can view the contents of the file and list the directory contents.
- w (write): Users with write permission can modify the file, including editing its contents, deleting it, or renaming it.
- x (execute): Users with execute permission can execute the file if it is a script or a binary executable.
File permissions are organized into three sets of three characters each, representing the permissions for the owner, group, and others. The order of the sets is as follows: owner, group, others. For each set, the three characters represent read, write, and execute permissions, respectively.
The permission characters are represented as follows:
- – (dash): Indicates that the permission is not granted.
- r (read): Indicates read permission.
- w (write): Indicates write permission.
- x (execute): Indicates execute permission.
- s (setuid/setgid): Indicates that the file has the setuid or setgid permission set.
- t (sticky bit): Indicates that the directory has the sticky bit set.
Here’s an example to illustrate file permissions:
-rwxr-x--- 1 user group 1024 May 1 09:30 script.sh
In this example, the file script.sh has the following permissions:
- The owner (
user) has read, write, and execute permissions (rwx). - The group (
group) has read and execute permissions (r-x). - Others have no permissions (
---).
To modify file permissions, you can use the chmod command. For example, to give read and write permissions to the owner of a file, you can use the command:
chmod u+rw file.txt
This command adds (+) read (r) and write (w) permissions to the user (u) of the file file.txt.
Understanding and managing file permissions is crucial for maintaining security and controlling access to files in a Unix-like system. It allows you to restrict or grant permissions to different users or groups based on their requirements.