Just recently started getting into OS X/iOS development and noticed several files have a "d" at the end. I.e launchd, accountsd, cloudd, assistantd, etc.. Not all have it just some. Just a quirky question I was pondering and figured if anyone knew the answer it would be you guys.

  • I'm gonna put this on hold because it's basically a trivia question. Asking why Apple does anything is generally off-topic as well. If there is a problem to be solved, adding that into the question will let us review the changes – bmike Nov 15 '15 at 18:43
  • It's not file name, the d stands for Daemon, which do background tasks. More info: developer.apple.com/library/mac/documentation/MacOSX/Conceptual/… – user14492 Nov 15 '15 at 18:49
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    Reopen. This is neither basic customer support nor recommendation inquiry. – Max Ried Nov 15 '15 at 19:10
  • This is a great question, because not all macOS users are former UNIX admins, Linux users, or NeXTstation owners. The "d" in the names is often helpful in figuring out what you are dealing with, often Apple has said nothing about these processes. – benc Jan 1 '19 at 22:21

Since OS X is in part based on FreeBSD here is relevant documentation from the FreeBSD Handbook's 3.8. Processes and Daemons...

"There is a convention to name programs that normally run as daemons with a trailing “d”. For example, BIND is the Berkeley Internet Name Domain, but the actual program that executes is named. The Apache web server program is httpd and the line printer spooling daemon is lpd. This is only a naming convention. For example, the main mail daemon for the Sendmail application is sendmail, and not maild."

Take note of the last two sentences from what I quoted, the trailing "d" is only a convention but as you can see with the example sendmail is the mail daemon and doesn't have the trailing "d". There are also other daemons in Unix/Unix like OSes that do not use the trailing "d" for daemons however as a convention it is a good practice but not an absolute.

  • A couple other helpful details. macOS came from Apple's acquisition of NeXT, which was a UNIX-based GUI OS. It had a lot of the expected UNIX daemons, but also added its own like netinfod. As Apple has developed macOS, it has created newer daemons, and they often follow the "ends-in-d" convention. – benc Jan 1 '19 at 22:19

Because it is a Unix pseudo-standard that daemons use that convention. Of course you already knew that, based on the tags you applied to the question.

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    "Of course you already knew that, based on the tags you applied to the question."... Just because Calculated used the daemons tag doesn't mean he/she knew why and if Calculated knew why then he/she probably would not have asked the question to begin with! ;) – user3439894 Nov 15 '15 at 18:02
  • Yea I just used the recommend tags. Thanks for the link on FreeBSD and the answer user3439894! – Calculated Nov 19 '15 at 14:44

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