645
rw-r--r-x
-rw-r--r-x
chmod 645 — the rw-r--r-x permission
645 is rw-r--r-x. The owner gets rw, and everyone else gets rx.
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 | ✓ | ✓ | · |
| Group4 | ✓ | · | · |
| Others5 | ✓ | · | ✓ |
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-r--r-x
- ls -l (file)
- -rw-r--r-x
- ls -l (directory)
- drw-r--r-x
- chmod symbolic form
- chmod u=rw,g=r,o=rx
- Command
- chmod 645 <file>
- Binary
- 110100101
- Decimal
- 421
- umask (directory)
- 132
- 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 645 mean?
It is rw-r--r-x. ls -l shows a file as -rw-r--r-x and a directory as drw-r--r-x.
Q. How is 645 written in rwx form?
It is the same as chmod u=rw,g=r,o=rx.
Q. What can other people do with 645?
They get r-x.
Q. Which umask produces 645?
132 for directories. For files it cannot be reached by umask alone, since new files never carry the execute bit.