| Class | Read | Write | Execute |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others |
— — About this tool
Unix permissions control who can read, write and execute a file. Each of the three groups — owner, group and others — has those three bits, written as an octal digit (rwx = 7) or symbolic letters (rwxr-xr-x). This calculator keeps a checkbox grid, the octal value and the symbolic notation in sync, so changing any one updates the others.
It also covers the special bits — setuid, setgid and the sticky bit — which add a fourth leading octal digit (as in 4755) and change the execute letters to s, S, t or T. Copy the ready-to-run chmod command, or paste an octal value to see exactly what it grants.
All calculation is local — nothing is uploaded.
Frequently asked questions
What does chmod 755 mean?
Owner gets read, write and execute (7); group and others get read and execute (5). It is the common mode for directories and executable scripts that everyone may run but only the owner may change.
What are setuid, setgid and the sticky bit?
They're special permission bits in a fourth octal digit. setuid/setgid run a file with its owner's or group's privileges; the sticky bit on a directory lets only a file's owner delete it. In symbolic form they replace the execute letter with s, S, t or T.
What's the difference between octal and symbolic notation?
They describe the same permissions two ways. Octal (755) is compact; symbolic (rwxr-xr-x) spells out each bit. chmod accepts both — this tool generates each from the checkbox grid.