Permission results
SecurePermission arithmetic
Owner: 4 + 2 + 1 = 7 Group: 4 + 0 + 1 = 5 Others: 4 + 0 + 1 = 5 Result: 755
Generated commands
chmod 755 filename
Common permission presets
Calculation history
Formula used
- Read contributes 4.
- Write contributes 2.
- Execute contributes 1.
- Each class total becomes one octal digit.
- Special bits form the leading fourth digit.
- File permissions equal 666 AND the inverted umask.
- Directory permissions equal 777 AND the inverted umask.
How to use
- Enter an octal value or choose permission checkboxes.
- Select special bits only when they are required.
- Choose a target type and enter its path.
- Review generated commands and security warnings carefully.
- Copy, export, print, or share the result.
Numeric permission examples
| Mode | Long format | Typical use |
|---|---|---|
| 600 | rw------- | Private user file |
| 644 | rw-r--r-- | Standard readable file |
| 700 | rwx------ | Private executable or directory |
| 755 | rwxr-xr-x | Publicly traversable directory |
| 775 | rwxrwxr-x | Group-managed directory |
| 1777 | rwxrwxrwt | Shared temporary directory |
Special permission guide
- Setuid changes effective user identity during execution.
- Setgid changes group identity or inherits directory groups.
- The sticky bit limits deletion inside shared directories.
- Lowercase s or t means execute is also enabled.
- Uppercase S or T means execute is disabled.
Frequently asked questions
What does CHMOD mean?
CHMOD changes file mode permissions on Unix-like systems. It controls reading, writing, and execution access. Always verify ownership before applying permissions to production files.
Why does 755 mean rwxr-xr-x?
Seven combines read, write, and execute permissions. Five combines read and execute permissions. The three digits represent owner, group, then other users.
Is 777 safe?
Mode 777 grants every permission to every user. It may expose files to unwanted modification. Use the narrowest permission level that still supports operations.
What is the difference between files and directories?
Read lists directory entries or reads file contents. Execute traverses directories or runs executable files. Write permits changes when ownership and directory rules allow.
What does a leading zero mean?
A leading zero commonly marks an octal number. Four-digit modes also include special permission bits. This calculator displays both compact and explicit octal forms.
What does setuid do?
Setuid runs an executable using its owner identity. Incorrect use can create serious privilege risks. Apply it only after a careful security review first.
What does setgid do on directories?
Setgid can make new entries inherit directory groups. It helps teams share managed project folders. Group membership and write access still require careful planning.
How does the sticky bit protect folders?
The sticky bit protects files within shared directories. Users cannot delete files owned by other users. System administrators commonly use it for temporary storage locations.
How does umask affect new files?
Umask removes permissions from system creation defaults. Files usually begin from 666, directories from 777. Applications may apply stricter permissions after creation as needed.
Can symbolic and octal modes be combined?
Commands normally use one permission expression at a time. Symbolic changes can modify only selected permission classes. Octal assignments immediately replace the complete permission set entirely.