Sticky Bits

• In addition to read, write, and execute permissions, there is a magic bit called the sticky bit. This bit applies only to directories.
• A directory that has the sticky bit set allows you to delete a file only if you are the owner of the file. As mentioned previously, you can ordinarily delete a file if you have write access to the directory that contains it, even if you are not the file's owner.
• When the sticky bit is set, you still must have write access to the directory, but you must also be the owner of the file that you want to delete.
• A few directories on the typical GNU/Linux system have the sticky bit set. For example, the /tmp directory, in which any user can place temporary files, has the sticky bit set.
• Only the owning user (or root, of course) can remove a file.

  $ ls -ld /tmp
  

• The corresponding constant to use with stat and chmod is S_ISVTX (Save text image after execution).
• If your program creates directories that behave like /tmp, in that lots of people put things there but shouldn't be able to remove each other's files, then you should set the sticky bit on the directory.

  $ chmod o+t directory
  chmod (dir_path, S_IRWXU | S_IRWXG | S_IRWXO | S_ISVTX);