CITS2002 Systems Programming  
← prev
next → CITS2002 CITS2002 schedule  

Copying strings

As strings are so important, the standard C library provides many functions to examine and manipulate strings.
However, C provides no basic string datatype, so we often need to treat strings as array of characters.

Consider these implementations of functions to copy one string into another: 

// DETERMINE THE STRING LENGTH, THEN USE A BOUNDED LOOP

void my_strcpy(char destination[], char source[])
{
    int length = strlen(source);

    for(int i = 0 ; i < length ; ++i) {
        destination[i] = source[i];
    }
    destination[length] = '\0';
}



// DO NOT WRITE STRING-PROCESSING LOOPS THIS WAY

void my_strcpy(char destination[], char source[])     
{
    int i;

    for(i = 0 ; i < strlen(source) ; ++i) {
        destination[i] = source[i];
    }
    destination[i] = '\0';
}



// USE AN UNBOUNDED LOOP, COPYING UNTIL THE NULL-BYTE  

void my_strcpy(char destination[], char source[])
{
    int  i = 0;

    while(source[i] != '\0') {
        destination[i] = source[i];
        i = i+1;
    }
    destination[i] = '\0';
}



// USE AN UNBOUNDED LOOP, COPYING UNTIL THE NULL-BYTE 

void my_strcpy(char destination[], char source[])
{
    int  i = 0;

    do {
        destination[i] = source[i];
        i = i+1;
    } while(source[i-1] != '\0');
}

 

CITS2002 Systems Programming, Lecture 6, p8, 8th August 2023.