Re: strncpy and 'n'

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: strncpy and 'n'
Date	2012-02-16 10:01 -0800
Organization	None to speak of
Message-ID	<lnvcn6fyi2.fsf@nuthaus.mib.org> (permalink)
References	<58d7c42a-7fd9-4507-bbe6-88941700b88a@k6g2000vbz.googlegroups.com>

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nroberts <roberts.noah@gmail.com> writes:
> Consider:
>
> char const* f(char const* incoming)
> {
>   static char buf[MAX];
>
>   strncpy(buf, incoming, strlen(incoming));
> }
>
> Is there ANY reason to use strncpy like that?  I'm working on a
> project that has such uses all throughout it and before I tell the
> team leader that he's using a basic C function incorrectly I thought
> I'd make sure I'm right.

There's rarely *any* reason to use strncpy().  It's not a "safer"
version of strcpy(); it's a quite different function.  It can leave
the target buffer without a terminating '\0' (i.e., not a string),
or it can pad it with multiple needless '\0' bytes.

For that particular call, if strlen(incoming) is 10, for example,
it will only copy 10 bytes; it will not copy the terminating '\0'.
If that's what you want (either buf doesn't need to be a string, or
some other code supplies the '\0'), then memcpy() makes more sense.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

strncpy and 'n' nroberts <roberts.noah@gmail.com> - 2012-02-16 09:05 -0800
  Re: strncpy and 'n' Anders Wegge Keller <wegge@wegge.dk> - 2012-02-16 18:57 +0100
    Re: strncpy and 'n' "A. K." <akk@nospam.org> - 2012-02-16 19:27 +0100
      Re: strncpy and 'n' Anders Wegge Keller <wegge@wegge.dk> - 2012-02-16 19:34 +0100
        Re: strncpy and 'n' "A. K." <akk@nospam.org> - 2012-02-16 20:58 +0100
  Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-16 10:01 -0800
    Re: strncpy and 'n' Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-16 11:10 -0800
      Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-16 14:20 -0800
        Re: strncpy and 'n' Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-17 04:19 -0800
          Re: strncpy and 'n' James Kuyper <jameskuyper@verizon.net> - 2012-02-17 10:04 -0500
            Re: strncpy and 'n' Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-17 10:27 -0800
            Re: strncpy and 'n' Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-17 11:22 -0800
              Re: strncpy and 'n' James Kuyper <jameskuyper@verizon.net> - 2012-02-17 14:40 -0500
                Re: strncpy and 'n' Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-18 02:17 -0800
    Re: strncpy and 'n' jgk@panix.com (Joe keane) - 2012-02-19 20:04 +0000
      Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-19 12:33 -0800
        Re: strncpy and 'n' jgk@panix.com (Joe keane) - 2012-02-20 21:25 +0000
          Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-20 14:46 -0800
            Re: strncpy and 'n' Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-23 23:13 +0000
              Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-23 16:20 -0800
              Re: strncpy and 'n' Philip Lantz <prl@canterey.us> - 2012-02-25 00:26 -0800
              Re: strncpy and 'n' pacman@kosh.dhis.org (Alan Curry) - 2012-02-26 01:34 +0000
                Re: strncpy and 'n' Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-28 22:46 +0000
                Re: strncpy and 'n' jgk@panix.com (Joe keane) - 2012-03-01 00:03 +0000
                Re: strncpy and 'n' Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-03-01 12:03 +0000
          Re: strncpy and 'n' James Kuyper <jameskuyper@verizon.net> - 2012-02-20 17:51 -0500
        Re: strncpy and 'n' Shao Miller <sha0.miller@gmail.com> - 2012-02-20 18:14 -0500
          Re: strncpy and 'n' pete <pfiland@mindspring.com> - 2012-02-20 23:16 -0500
            Re: strncpy and 'n' Shao Miller <sha0.miller@gmail.com> - 2012-02-25 01:51 -0500
              Re: strncpy and 'n' pete <pfiland@mindspring.com> - 2012-02-25 10:34 -0500
        Re: strncpy and 'n' Rich Webb <bbew.ar@mapson.nozirev.ten> - 2012-02-20 19:09 -0500
          Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-20 16:46 -0800
            Re: strncpy and 'n' Rich Webb <bbew.ar@mapson.nozirev.ten> - 2012-02-20 20:48 -0500
          Re: strncpy and 'n' Shao Miller <sha0.miller@gmail.com> - 2012-02-20 19:46 -0500
        Re: strncpy and 'n' jgk@panix.com (Joe keane) - 2012-02-21 21:46 +0000
          Re: strncpy and 'n' James Kuyper <jameskuyper@verizon.net> - 2012-02-21 17:15 -0500
          Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-21 14:29 -0800
            Re: strncpy and 'n' Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-02-22 01:15 -0800
            Re: strncpy and 'n' jgk@panix.com (Joe keane) - 2012-02-23 00:02 +0000
              Re: strncpy and 'n' Keith Thompson <kst-u@mib.org> - 2012-02-22 17:02 -0800
  Re: strncpy and 'n' Markus Schaub <usenet@markus-schaub.de> - 2012-02-16 18:53 +0000
  Re: strncpy and 'n' lawrence.jones@siemens.com - 2012-02-16 13:25 -0500
  Re: strncpy and 'n' blp@cs.stanford.edu (Ben Pfaff) - 2012-02-16 11:18 -0800
  Re: strncpy and 'n' Stephen Sprunk <stephen@sprunk.org> - 2012-02-16 13:29 -0600
    Re: strncpy and 'n' Ike Naar <ike@iceland.freeshell.org> - 2012-02-16 22:45 +0000
  Re: strncpy and 'n' ImpalerCore <jadill33@gmail.com> - 2012-02-16 11:32 -0800
  Re: strncpy and 'n' Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-17 00:50 -0800

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