661
rw-rw---x
-rw-rw---x
chmod 661 — the rw-rw---x permission
661 is rw-rw---x. The owner gets rw, and everyone else gets x.
Who can do what
Three rows for owner, group and others; three columns for read, write and execute. On a folder that last one means the right to go inside.
| Read | Write | Execute | |
|---|---|---|---|
| Owner6 | ✓ | ✓ | · |
| Group6 | ✓ | ✓ | · |
| Others1 | · | · | ✓ |
On a folder the execute bit means going inside. With read but no execute you can list the names yet open nothing in it.
- Symbolic
- rw-rw---x
- ls -l (file)
- -rw-rw---x
- ls -l (directory)
- drw-rw---x
- chmod symbolic form
- chmod u=rw,g=rw,o=x
- Command
- chmod 661 <file>
- Binary
- 110110001
- Decimal
- 433
- umask (directory)
- 116
- umask (file)
- Not reachable — new files never start with the execute bit
One digit away
How to read this
- Read is 4, write 2, execute 1; add them for one digit. 7 is 4+2+1, 5 is 4+1.
- The digits are owner, group, others, left to right.
- umask is what gets taken away: from 777 for directories, from 666 for files.
- Special bits (setuid 4000, setgid 2000, sticky 1000) add a fourth digit in front — /tmp is 1777.
Frequently asked questions
Q. What does chmod 661 mean?
It is rw-rw---x. ls -l shows a file as -rw-rw---x and a directory as drw-rw---x.
Q. How is 661 written in rwx form?
It is the same as chmod u=rw,g=rw,o=x.
Q. What can other people do with 661?
They get --x.
Q. Which umask produces 661?
116 for directories. For files it cannot be reached by umask alone, since new files never carry the execute bit.