Chmod Calculator

chmod (change mode) is a Unix/Linux command used to change the access permissions of files and directories. It controls who can read, write, or execute a file using a numeric (octal) or symbolic notation.

Each digit represents permissions for a group: the first digit is the owner, the second is the group, and the third is others. Read is 4, write is 2, and execute is 1. These values are added together, so 7 means read+write+execute (4+2+1).

644 (rw-r--r--) gives the owner read and write access while group and others can only read. 755 (rwxr-xr-x) gives the owner full access and allows group and others to read and execute. 644 is typical for files, 755 for directories and scripts.

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Symbolic notation uses letters to represent permissions: r for read, w for write, and x for execute. Each set of three characters represents owner, group, and others. For example, rwxr-xr-- means the owner has full access, the group can read and execute, and others can only read.