The nitty gritty of Unix rights management

Bonus Points

Job candidates receive bonus points if they can explain when Unix displays a directory's sticky bit with t and when with T. The hack with the sticky bit covers the bit that actually displays general execution rights to the directory with the final t in rwt. It is no longer possible to say whether rw- or rwx was configured before the sticky bit was turned on. Unix therefore displays rwt if rwx was present and displays rwT if execute permissions are missing – that is, if rw- existed previously.

Those who also know that not just directories, but also files, can take a sticky bit – which, however, controls something completely different – will demonstrate that they have taken their preparation seriously and have studied Kerrisk's book. These candidates are sure to score 100 points and make it to the next round!

Infos

  1. Listings for this article: ftp://ftp.linux-magazine.com/pub/listings/magazine/177
  2. Kerrisk, Michael. The Linux Programming Interface: A Linux and UNIX System Programming Handbook. No Starch Press, 2010.

The Author

Mike Schilli works as a software engineer in the San Francisco Bay Area. He can be contacted at mailto:mschilli@perlmeister.com. Mike's homepage can be found at http://perlmeister.com.

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