Chmod Calculator
Calculate Unix/Linux file permissions
644-rw-r--r--chmod 644🔐 Permissions
| Read (r) | Write (w) | Execute (x) | Value | |
|---|---|---|---|---|
| 👤 Owner (u) | 6 | |||
| 👥 Group (g) | 4 | |||
| 🌍 Other (o) | 4 |
Special Bits
🔢 Numeric Input
3-digit (755) or 4-digit with special bits (4755)
⚡ Common Presets
📊 Permission Values
| Symbol | Value | Meaning |
|---|---|---|
| r | 4 | Read |
| w | 2 | Write |
| x | 1 | Execute |
| - | 0 | No permission |
🔑 Special Bits
| Bit | Value | Description |
|---|---|---|
| SetUID (s) | 4 | Execute as owner |
| SetGID (s) | 2 | Execute as group |
| Sticky (t) | 1 | Only owner can delete |
📝 Symbolic Notation Explanation
- (file)
d (dir)
rwx = 7
r-x = 5
r-- = 4
How to Calculate File Permissions
- Toggle permission checkboxes for Owner, Group, and Others
- Or enter a numeric value (e.g., 755) directly
- See the symbolic notation update in real-time
- Copy the chmod command for your terminal
- Use common presets for standard permission sets
Frequently Asked Questions
What does chmod 755 mean?
755 means: Owner can read/write/execute (7), Group can read/execute (5), Others can read/execute (5). Common for directories and executable scripts.
What's the difference between 644 and 755?
644 (rw-r--r--) is for regular files - owner can read/write, others can only read. 755 (rwxr-xr-x) adds execute permission, needed for directories and scripts.
What are special permission bits?
Special bits include: Setuid (4xxx) - run as owner, Setgid (2xxx) - run as group, Sticky bit (1xxx) - only owner can delete. Used for special system requirements.
Why is chmod 777 dangerous?
777 gives everyone full read/write/execute access. This is a security risk as any user or process can modify or delete the file. Avoid on production systems.
How do I read symbolic notation?
Symbolic notation like 'rwxr-xr--' shows permissions in groups of 3: owner (rwx), group (r-x), others (r--). r=read, w=write, x=execute, -=no permission.
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