Chmod Calculator

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Chmod Calculator

Calculate and convert Unix/Linux file permissions between octal (755) and symbolic (-rwxr-xr-x) formats.

Permission Configuration

Octal Format

Numeric representation (e.g., 755)

Symbolic Format

Character representation (e.g., -rwxr-xr-x)

Permission Explanation

The permission set 755 (-rwxr-xr-x) means:

Owner: can read, write, execute
Group: can read, execute
Other: can read, execute

What

Chmod Calculator definition

chmod permissions represent read/write/execute access in octal or symbolic form.

Cases

Use Cases

Convert rwx permissions to octal

Understand file access for users and groups

Set executable permissions correctly

How To

How to Calculate chmod Permissions

A step-by-step guide to converting between octal and symbolic permissions.

Choose input type

Pick octal (e.g., 755) or symbolic (e.g., -rwxr-xr-x) input.

Set permissions

Toggle read/write/execute for owner, group, and others (or paste a value).

Copy results

Review the converted output and copy the format you need.

Knowledge

Understanding Unix File Permissions

What are File Permissions?

Unix file permissions control who can read, write, or execute files. Each file has three permission sets: owner (user who created the file), group (users in the file's group), and others (everyone else).

Permission Types

Read (r/4) allows viewing file contents or listing directory contents. Write (w/2) allows modifying files or creating/deleting files in directories. Execute (x/1) allows running files as programs or accessing directories.

Octal Notation

Permissions are often expressed as three octal digits. Each digit (0-7) is the sum of: read (4) + write (2) + execute (1). So 755 means owner=rwx(7), group=rx(5), others=rx(5).

Special Permissions

Beyond basic permissions: setuid (4) runs executable as owner, setgid (2) runs as group or inherits directory group, sticky bit (1) restricts deletion in shared directories. These add a fourth leading digit.

Directory Permissions

Directory permissions work differently: read lets you list contents, write lets you create/delete files inside, execute lets you access (cd into) the directory. A directory needs execute for any access to its contents.

FAQ

Frequently Asked Questions

What is Unix?

Unix is a powerful, multitasking, multi-user computer operating system that was originally developed at Bell Labs. Many modern operating systems, including Linux and macOS, are based on Unix principles.

What are File Permissions?

File permissions determine who can read, write, or execute a file. In Unix-like systems, these are managed for three categories of users: the file owner, the group owner, and others.

What is Chmod?

chmod (change mode) is a command-line utility in Unix-like operating systems used to change the access permissions of file system objects (files and directories).

How do Octal permissions work?

Octal permissions use numbers 0-7 to represent permissions. Read=4, Write=2, Execute=1. These are summed up. For example, 7 = 4+2+1 (Read+Write+Execute), 5 = 4+1 (Read+Execute).

What are Symbolic permissions?

Symbolic permissions use characters to represent access rights: 'r' for read, 'w' for write, 'x' for execute, and '-' for no permission. They are grouped for owner, group, and others.

What are common permission settings?

Common settings include: 755 (rwxr-xr-x) for scripts/programs (owner all, others read/execute), 644 (rw-r--r--) for files (owner read/write, others read only), and 777 (rwxrwxrwx) for full access to everyone (use with caution).