Chmod Calculator
Convert Unix file permissions between octal and rwx symbolic notation.
| Permission | Owner | Group | Others |
|---|---|---|---|
| Read | |||
| Write | |||
| Execute |
Octal
755Symbolic
rwxr-xr-xCommand
chmod 755 fileFormula & methodology
Each permission class (owner, group, others) is a 3-bit value where read=4, write=2, execute=1. The optional leading digit encodes setuid=4, setgid=2 and sticky=1.
Worked example
- 755 → rwxr-xr-x · chmod 755 file
- rw-r--r-- → 644
Frequently asked questions
What does chmod 755 mean?
The owner can read, write and execute (7), while group and others can read and execute but not write (5). It is common for scripts and directories.
What is the fourth (leading) digit?
It sets special bits: 4 = setuid, 2 = setgid, 1 = sticky. For example 4755 sets the setuid bit on an otherwise 755 file.
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