Home Accessibility Courses Twitter The Mouth Facebook Resources Site Map About Us Contact
 
NEW SERVER - 11.9.2020 ... Retiring, March 2020 - sorry, you have missed our final public course.
The Coronavirus situation has lead us to suspend public training - which was on the cards anyway, with no plans to resume

Please ask about private 'maintenance' training for Python, Tcl, Perl, PHP, Lua, etc
Happily continuing private consultancy / programming work
 
String compare and copy
Character Strings example from a Well House Consultants training course
More on Character Strings [link]

This example is described in the following article(s):
   • Strings in C - strncmp strncpy and friends - [link]

Source code: s1.c Module: C206
/* Strings in C are pointers to arrays of characters, null (\0) terminated.
Which means that if you compare them with the == operator, you're going to be
comparing addresses, and not whether the strings contain the same text. And even
if you put a "*" in front of the variable you're comparing, all you'll do is compare
the first character.

Solution is to use standard functions such as strcmp and strcpy - string compare and
string copy. Both of these are regarded as dangerous as they can run off the end of
stings that aren't properly null terminated, so you also have strncmp and strncpy
which are better regarded, and have an extra parameter which is the maximum number of
characters to compare / copy.

Similarly, fgets to read in a string (use stdin for the keyboard) with a maximum length
is much safer that gets which can easiiy be overrun by a too-long input! */


#include <stdio.h>
#include <strings.h>

int main() {
        char saying[81];
        char host[81];
        int i;

        for (i=0; i<2; i++) {
                printf("Whats yaname: ");
                fgets(saying,80,stdin);

                /* add a "null" in the last place to replace the new line that
                fgets adds (well - the user adds to indicate his response is complete! ) */


                saying[strlen(saying)-1] = '\0';

                printf("You said %s to me\n",saying);

                if (! strncmp(saying,"Graham",80)) {
                        printf("It's your party\n");
                } else {
                        printf("Don't forget the booze\n");
                }
                if (i == 0) strncpy(host,saying,80);
        }
        printf("Party %s and %s\n",host,saying);
}

/* Sample Output

WomanWithCat:harwell grahamellis$ ./s1
Whats yaname: Graham
You said Graham to me
It's your party
Whats yaname: Robert
You said Robert to me
Don't forget the booze
Party Graham and Robert
WomanWithCat:harwell grahamellis$

*/

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to Program in C
 * Learning to program in C and C++
 * Programming in C
 * C and C++ Programming
 * Learning to program in C and C++
 * C and C++ Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering C and C++ are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Character Strings" training module. You'll find a description of the topic and some other closely related examples on the "Character Strings" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Purpose of this website
This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Web site author
This web site is written and maintained by Well House Consultants.

Conditions of use
Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.

You can Add a comment or ranking to this page

© WELL HOUSE CONSULTANTS LTD., 2020: 48 Spa Road • Melksham, Wiltshire • United Kingdom • SN12 7NY
PH: 01144 1225 708225 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho

PAGE: http://www.wellho.net/resources/ex.php • PAGE BUILT: Mon Sep 28 10:27:35 2020 • BUILD SYSTEM: JelliaJamb