C String: String Concat (Simple Note)

Simple Note

Code

#include <stdio.h>
#include <string.h>
/**
 * 
 * Tested with Dev-C++ 4.9.9.2
 *  
 * Practice of string copy and concat.
 * char * strcat ( char * destination, const char * source );
 *         Appends a copy of the source string to the destination string
 *         plus a terminating null-character if source contains null-character.
 * char * strncat ( char * destination, char * source, size_t num );
 *         Appends the first num characters of source to destination,
 *         plus a terminating null-character.
 *
 * Note: 
 * 
 */
int main () {
    // a char array without '\0'
    char chArr[4] = {'a', 'b', 'c', 'd'};
    char chArrTwo[20] = "mnopq";
    char chArrThree[] = "abcd";
    char chArrFour[20] = "wxyz";

    // the source (chArr) doesn't have null-char ('\0')
    // will become wrong value after first concat
    printf("original: %s\n", chArrTwo);
    strcat(chArrTwo, chArr); // <-- the line above
    // change the line above to the line below then everything should be okay.
    // strncat(chArrTwo, chArr, 4); // <-- the line below
    printf("append abcd: %s\n", chArrTwo);
    strncat(chArrTwo, chArr, 2);
    printf("append ab: %s\n\n", chArrTwo);

    // the source (chArrThree) contains null-char ('\0')
    // everything should be okay
    printf("original: %s\n", chArrFour);
    strcat(chArrFour, chArrThree);
    printf("append abcd: %s\n", chArrFour);
    strncat(chArrFour, chArrThree, 2);
    printf("append ab: %s\n\n", chArrFour);

    system("PAUSE");
}

Result

References

strcat
http://www.cplusplus.com/reference/cstring/strcat/

strncat
http://www.cplusplus.com/reference/cstring/strncat/

Download

Source code at github
https://github.com/benbai123/C_Cplusplus_Practice/blob/master/C_StringProcessing/string_concat.c