0755

0755 is a common octal file permission notation used in Unix-like operating systems to specify how files and directories may be accessed. The leading zero indicates that the value is in octal notation, as opposed to decimal. It is widely used with the chmod command and appears in archive metadata and software packaging. In programming contexts, 0755 may also be written as 0o755 (Python) or simply 755 when used with shell tools.

The digits describe access for three classes: owner, group, and others. Each digit is the sum of permission bits: read (4), write (2), and execute (1). Therefore, 7 equals rwx, and 5 equals r-x. Consequently, 0755 grants the owner full read, write, and execute permissions, while group and others have read and execute permissions only. For directories, the execute bit allows entering the directory and traversing its contents; for files, execute permits running the file as a program or script.

Usage and implications: 0755 is a common default for executable programs and scripts that should be accessible to all users, such as binaries installed system-wide or scripts in /usr/bin. It is less restrictive than 0644 or 0600, which remove write or execute permissions for some classes. When distributing software, 0755 helps ensure that components can be executed after extraction, while still preventing unauthorized modification by non-owners.