Interesting results for getservbyname() performance (and possible changes for /etc/services)

Nils Philippsen nphilipp at
Thu Jan 12 13:10:22 UTC 2006

On Thu, 2006-01-12 at 06:36 -0500, Ignacio Vazquez-Abrams wrote:
> On Thu, 2006-01-12 at 12:02 +0100, Phil Knirsch wrote:
> > Now, i know and understand how and why glibc does the getservbyname() 
> > call as it does (namely, every time opening, reading and parsing the 
> > file). It neither caches calls nor does any other fancy stuff (how could 
> > it? The order in the file is arbitrary, so the only possibility is to do 
> > a linear read and parse of the file).
> > Comments and suggestions are of course always welcome.
> What about writing (or finding) a NS module that does caching? It can
> pull from a sorted bdb using a binary search, unless /etc/services is
> newer at which point it rebuilds the database. /etc/services almost
> *never* changes, so the rebuild speed shouldn't matter too much.

Well, it can't be done this way because NS modules are running with the
user's privileges. This would have to be handed off to a daemon with the
privileges necessary.

     Nils Philippsen    /    Red Hat    /    nphilipp at
"They that can give up essential liberty to obtain a little temporary
 safety deserve neither liberty nor safety."     -- B. Franklin, 1759
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