strnlen — determine the length of a fixed-size string
#define _GNU_SOURCE #include <string.h>
size_t strnlen( | 
            const char * | s, | 
| size_t | maxlen); | 
          
The strnlen() function
      returns the number of characters in the string pointed to by
      s, not including the
      terminating '\0' character, but at most maxlen. In doing this,
      strnlen() looks only at the
      first maxlen
      characters at s and
      never beyond s+maxlen.
The strnlen() function
      returns strlen(s),
      if that is less than maxlen, or maxlen if there is no '\0'
      character among the first maxlen characters pointed to by
      s.
This page is part of release 2.79 of the Linux man-pages project. A
      description of the project, and information about reporting
      bugs, can be found at
      http://www.kernel.org/doc/man-pages/.
| 
                 Copyright (c) Bruno Haible <haibleclisp.cons.org> This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. References consulted: GNU glibc-2 source code and manual  |