chmod 755 rwxr-xr-x

chmod 755 (rwxr-xr-x): the owner can read, write and execute; group and others can read and execute. Typical use: directories, programs and scripts.

Octal: 755 (also written 0755)
Symbolic: rwxr-xr-x
ls -l shows: -rwxr-xr-x for a file, drwxr-xr-x for a directory
chmod letters: u=rwx,g=rx,o=rx

Who can do what

Class	Digit	Bits	On a file	On a directory
Owner (u)	7	`rwx`	Read the contents, change or empty the contents and run it as a program	List the names inside, create, delete and rename entries and enter it and open files by name
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

The owner has full access, everyone else can read and execute. New directories get it under umask 022, and it is the standard mode for programs in /usr/bin, shell scripts, and web directories (WordPress recommends 755 for folders and 644 for files).

Security notes

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 755 file
Symbolic
chmod u=rwx,g=rx,o=rx file
Check the result
stat -c '%a %A %n' file
Directories only, recursively
find /path -type d -exec chmod 755 {} +

Avoid chmod -R 755 on a tree that holds files as well as folders: it makes every file executable. Use the find command above for directories and a file mode such as 644 for the files.

The umask that gives 755

umask 022: new directories are created as 755 (and files as 644)

Programs create files with 666 and directories with 777, and the umask removes bits from those. A umask never adds execute to a new file, and it cannot set setuid, setgid or the sticky bit.

Its file counterpart is chmod 644 (rw-r--r--).

Other common modes

Work out any other mode in the chmod calculator