What are Unix file permissions?

Unix permissions control who can read, write, or execute a file. Each file has permissions for the owner, group, and others.

755 means: owner can read+write+execute (7), group can read+execute (5), others can read+execute (5).

What does the leading 'd' mean?

The 'd' indicates a directory. Regular files show '-'. Other types include 'l' (symlink), 'c' (character device), 'b' (block device).

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