If a directory is writable and has sticky bit is set, files within directory removed or renamed only if one or more following is true:

- The user owns the file

- The user owns the directory

- The file writable by the User

- The user is "root"

chmod 1777 project_dir

The sticky bit is displayed as the letter t in the execute field for 'others'.

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Sticky Bit is a permission bit that protects the files with in a Directory. If the directory has sticky bit set, a file can be deleted by the owner of the file, the owner of the directory or root.

This Prevents a user from deleting other users files from public directories .