chmod 166 Permission Explained
Summary: chmod 166 gives the owner execute, the group read/write, and everyone else read/write.
| Class | Read (4) | Write (2) | Execute (1) | Octal |
|---|---|---|---|---|
| Owner (u) | 1 | |||
| Group (g) | 6 | |||
| Others (o) | 6 |
chmod 166 filename
chmod 166 Breakdown
| Class | Digit | Symbolic | On a file | On a directory |
|---|---|---|---|---|
| Owner (u) | 1 |
--x |
Execute only | Can enter (cd) but not list contents |
| Group (g) | 6 |
rw- |
Read and write | Can list names, cannot enter |
| Others (o) | 6 |
rw- |
Read and write | Can list names, cannot enter |
Is chmod 166 Safe?
Critical Risk
- Anyone on the system can modify or replace this file.
- Every member of the group can modify this file.
- Any user can read this file — never use it for secrets such as keys or .env files.
- Even the owner cannot modify this file without changing permissions first.
- Scripts need read permission to run; only compiled binaries can be executed without it.
- Unusual: a lower class has permissions the class above it lacks.
Common Use Cases
166 is uncommon in standard Linux setups. The closest widely used permission is chmod 666.
chmod 166 Command Examples
# Apply using octal mode
chmod 166 filename
# Apply using equivalent symbolic mode
chmod u=x,g=rw,o=rw filename
# Recursive command warning:
chmod -R 166 /path/to/dir
# Note: -R applies the same mode to files and directories. Use find to treat them separately:
find /path/to/dir -type d -exec chmod 166 {} +
# Verify permissions
stat -c '%a %A %n' filename # Linux
stat -f '%Lp %Sp %N' filename # macOS
# Example ls -l output:
---xrw-rw- 1 alice staff 1024 Jan 15 10:00 example.txtumask Relationship
A umask of 611 makes new directories 166. Test umask values with our interactive Umask Calculator.
Frequently Asked Questions
What does chmod 166 mean?
chmod 166 gives the owner execute, the group read/write, and everyone else read/write. In octal notation, the owner receives 1 (execute), the group receives 6 (read/write), and others receive 6 (read/write).
Is chmod 166 safe?
chmod 166 is classified as Critical Risk. Anyone on the system can modify or replace this file.
What is chmod 166 in symbolic notation?
In symbolic notation, chmod 166 is represented as --xrw-rw-. You can apply this permission using the equivalent symbolic command "chmod u=x,g=rw,o=rw filename".
Related Permissions
Change one bit: