Overview
Builds Linux file permissions with checkboxes instead of mental octal arithmetic: three groups (owner, group, public) of read/write/execute toggles, the setuid/setgid/sticky special bits, and presets for the modes everyone types from memory.
How It Works
Tick the permission boxes per group; the octal and symbolic readouts update as you go. Six preset buttons — 755, 644, 600, 777, 700, 666 — load common configurations instantly. Copy octal puts the 4-digit value (special-bit digit included, e.g. 0755) on your clipboard, and the usage hint shows the ready-to-paste chmod command.
Step-by-Step Usage Guide
- Tick Read, Write, and Execute for Owner, Group, and Public.
- Add special bits only if you specifically need setuid, setgid, or the sticky bit.
- Compare the Octal and Symbolic readouts, then copy the octal value.
- Run the suggested chmod command on your target file.
Technical Specifications & Standards
Each group contributes 4 for read, 2 for write, and 1 for execute; the displayed octal is the special-bit digit followed by the three group digits. The symbolic readout renders in the familiar rwx shape — setuid appears as an s in the owner-execute position, while setgid and sticky currently surface only in the octal prefix. Loading a preset is also a way to see what 755 actually means: read-write-execute for the owner, read-execute for everyone else.
Targeted Use Cases
- Working out the mode for a deploy script that must be executable but not world-writable.
- Checking what a 664 versus 644 difference actually grants before applying it to shared files.
- Understanding special-bit modes such as the sticky bit on /tmp (1777).
- Teaching or documenting permissions with a visual bit-to-octal mapping.
Notes & Gotchas
- There is no octal input: arbitrary modes are set through the checkboxes or the six presets. Compose unusual modes such as 2750 or 1777 by ticking the special bits yourself.
- SetGID and Sticky affect only the octal prefix, not the symbolic letters — verify special-bit changes with ls -l after applying them.
- Directories typically need execute to be traversable, which is why 755 is the common preset; the calculator shows the leading dash symbolic shape of a file.
- chmod applies to what you run it on — there is no -R recursion here. Combine the copied octal with chmod -R yourself when changing whole trees.
Frequently Asked Questions
How do the numbers relate to the checkboxes?
Read is 4, write is 2, execute is 1; each group's digit is the sum of its ticks, and the first digit is setuid (4) plus setgid (2) plus sticky (1).
Why does the octal show four digits, like 0755?
The first digit carries the special bits. When it is zero you can safely use just the trailing three digits with chmod.
Can I paste an octal mode in?
No. Input is checkbox-and-preset only — the tool is for constructing and understanding modes, not parsing them.
Does it work offline?
Yes. The arithmetic is a few sums in your browser; nothing is looked up or sent anywhere.