chmod and umask

Type chmod for an editor, or chmod 755 to start from a mode. Tick the boxes or type the octal, and copy the command.

The editor

• A grid of read, write and execute for owner, group and others, plus setuid, setgid and sticky.
• The octal field (type 644, 0755 or 4755) and the symbolic form (rwxr-xr-x), each kept in step with the boxes.
• A command such as chmod 755 file, with a box for the file name. Ctrl+Enter copies it.
• Plain English underneath: Owner: read, write and execute, and a note for well-known modes (644 is the usual mode for a file, 777 is rarely a good idea).

What you can type

Type	Means
chmod 755, chmod 0644, chmod 4755	An octal mode
chmod rwxr-xr-x, chmod -rw-r--r--	A symbolic mode (an ls -l string, with or without the file type)
chmod u+x,g-w,o=r	Symbolic clauses, applied to nothing (000)
chmod 644 u+x	A mode followed by clauses
umask 022	The permissions new files and directories get

Clauses work like chmod: u, g, o and a for who, +, - and = for what, and r, w, x, X, s, t or another class (g=u). No umask is applied when the “who” is left out; everything is treated as a.

umask

umask 022 shows 644 for new files (they start from 666) and 755 for new directories (they start from 777). Any three octal digits work.

Everything is worked out in your browser. Copied commands are saved in Recent. The tools are also widgets: chmod calculator and umask calculator.