umask command in Linux and it perimeters

The umask command in Linux is used to set the default file permission mask for newly created files and directories. It helps control the permissions that are automatically applied when a new file or directory is created. The umask value is subtracted from the maximum permissions (usually 666 for files and 777 for directories) to determine the final permissions for the newly created files and directories.

Here’s a table explaining the umask command parameters and options:

Now, let’s see some examples of how to use the umask command:

1. Set the umask value using an octal representation:

umask 0022

In this example, the umask value is set to 0022, meaning that newly created files will have permissions of 644 (666 – 0022) and directories will have permissions of 755 (777 – 0022).

2. Set the umask value using a symbolic representation:

umask u=rwx,g=rx,o=rx

In this example, the umask value is set to u=rwx,g=rx,o=rx, meaning that newly created files will have permissions of 755 (777 – u=rwx) and directories will have permissions of 755 (777 – u=rwx).

3. Display the current umask value in symbolic form:

umask -S

Output:

u=rwx,g=rx,o=rx

This command displays the current umask value in symbolic form, showing the permissions that will be removed when creating new files and directories.

4. Display the current umask value in a human-readable format:

umask -p

Output:

0022

This command displays the current umask value in a human-readable format (octal representation).

By setting the appropriate umask value, you can control the default permissions for newly created files and directories, ensuring the security and privacy of sensitive data and avoiding unnecessary exposure of files and directories to other users.