Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #17719

Re: strncpy and 'n'

Show all headers | View raw

Rich Webb <bbew.ar@mapson.nozirev.ten> writes:
[...]
> I'm surprised that the construct
>
>    strncpy(dest, source, BUF_LEN)[BUF_LEN - 1] = '\0';
>
> hasn't been mentioned. It seems to be a reasonably compact way of
> dealing with uncontrolled input.

Yes, that should work.  (I've never seen anyone actually use that
idiom; have you?)

Note that if dest is, say, 1000 bytes, and strlen(source)==3,
then it will write 997 null characters into dest, when 1 would do.
If the source string is from user or file input, that's probably
not going to be significant.

This avoids that problem:

    dest[0] = '\0';
    strncat(dest, source, BUF_LEN - 1);

Another problem is that it *silently* truncates overly long input.
(That might be just what you want.)

The problems of strncat can be worked around if you're aware of them,
but I'm skeptical that it's worth the effort.

-- 
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"

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

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

csiph-web