Permissions
Tick the boxes or type an octal or symbolic value. All three stay in sync.
Read
Write
Execute
Owneruser (6)
Groupmembers (4)
Otherseveryone else (4)
Special bits
Runs as the file owner
Runs as the file group
Restricts deleting in a directory
Presets
Regular file. Owner can edit; everyone else can only read. The usual default for files.
Octal and symbolic
A fourth leading digit sets the special bits: 4 setuid, 2 setgid, 1 sticky. In the symbolic form, s and t mean the bit and execute are both set; capital S and T mean the bit is set without execute. You can also paste the 10 characters from ls -l.
Commands
Copy the one you prefer.
Numeric
chmod 644 file
Symbolic
chmod u=rw,g=r,o=r file
Who can do what
- Owner (user) can read and write but cannot execute.
- Group can read but cannot write or execute.
- Others (everyone else) can read but cannot write or execute.
On a directory, read lists its entries, write adds, renames and removes entries, and execute lets you enter it and reach what is inside.