chmod 655 rw-r-xr-x

chmod 655 (rw-r-xr-x): the owner can read and write; group and others can read and execute. Typical use: a likely typo for 755. Commands and umask.

Octal: 655 (also written 0655)
Symbolic: rw-r-xr-x
ls -l shows: -rw-r-xr-x for a file, drw-r-xr-x for a directory
chmod letters: u=rw,g=rx,o=rx

Who can do what

Class	Digit	Bits	On a file	On a directory
Owner (u)	6	`rw-`	Read the contents and change or empty the contents	List the names inside, nothing more with write alone (it needs execute to work) and see names only, not open or inspect the files
Group (g)	5	`r-x`	Read the contents and run it as a program	List the names inside and enter it and open files by name
Others (o)	5	`r-x`	Read the contents and run it as a program	List the names inside and enter it and open files by name

Each digit adds read (4), write (2) and execute (1). Deleting or renaming a file depends on write and execute on the directory that holds it, not on the file's own mode. Root bypasses read and write checks.

Typical uses

An unusual mode: the owner can read and write but not execute, while the group and others can read and execute. It is almost always a typo for 755 or 644. Linux checks only the owner bits when the owner opens the file, so the owner cannot run it even though everyone else can.

Security notes

The owner has fewer rights than the group or others. Linux checks the owner bits alone for the owner, so the owner is the one locked out, which is rarely intended.
Only the owner (and root) can change it; the group and others are limited to the read and execute rights shown above, which is the usual safe pattern for shared files and directories.
Every account on the machine can read it, so keep passwords, keys and tokens out of anything with this mode.

Commands

Numeric
chmod 655 file
Symbolic
chmod u=rw,g=rx,o=rx file
Check the result
stat -c '%a %A %n' file
Files only, recursively
find /path -type f -exec chmod 655 {} +

The umask that gives 655

No umask produces 655: a umask only removes bits from 666 for files and 777 for directories, and it never sets execute on a new file. Set it with chmod after creating the file or directory.

Other common modes

Work out any other mode in the chmod calculator