chmod 042 Permission Explained
Summary: chmod 042 gives the owner no access, the group read, and everyone else write.
| Class | Read (4) | Write (2) | Execute (1) | Octal |
|---|---|---|---|---|
| Owner (u) | 0 | |||
| Group (g) | 4 | |||
| Others (o) | 2 |
chmod 042 filename
chmod 042 Breakdown
| Class | Digit | Symbolic | On a file | On a directory |
|---|---|---|---|---|
| Owner (u) | 0 |
--- |
No access | Cannot list, enter, or modify |
| Group (g) | 4 |
r-- |
Read only | Can list names, but not enter |
| Others (o) | 2 |
-w- |
Write only (rarely useful) | No practical effect without x |
Is chmod 042 Safe?
Critical Risk
- Anyone on the system can modify or replace this file.
- Even the owner cannot modify this file without changing permissions first.
- Unusual: a lower class has permissions the class above it lacks.
Common Use Cases
042 is uncommon in standard Linux setups. The closest widely used permission is chmod 440.
chmod 042 Command Examples
# Apply using octal mode
chmod 042 filename
# Apply using equivalent symbolic mode
chmod u=,g=r,o=w filename
# Recursive command warning:
chmod -R 042 /path/to/dir
# Note: -R applies the same mode to files and directories. Use find to treat them separately:
find /path/to/dir -type f -exec chmod 042 {} +
# Verify permissions
stat -c '%a %A %n' filename # Linux
stat -f '%Lp %Sp %N' filename # macOS
# Example ls -l output:
----r---w- 1 alice staff 1024 Jan 15 10:00 example.txtumask Relationship
A umask of 735 makes new directories 042 and new files 042. Test umask values with our interactive Umask Calculator.
Frequently Asked Questions
What does chmod 042 mean?
chmod 042 gives the owner no access, the group read, and everyone else write. In octal notation, the owner receives 0 (no access), the group receives 4 (read), and others receive 2 (write).
Is chmod 042 safe?
chmod 042 is classified as Critical Risk. Anyone on the system can modify or replace this file.
What is chmod 042 in symbolic notation?
In symbolic notation, chmod 042 is represented as ---r---w-. You can apply this permission using the equivalent symbolic command "chmod u=,g=r,o=w filename".
Related Permissions
Change one bit: