strcpy vs. memcpy

What is the difference between memcpy() and strcpy()? I tried to find it with the help of a program but both are giving the same output.

int main()
{
    char s[5]={'s','a','\0','c','h'};
    char p[5];
    char t[5];
    strcpy(p,s);
    memcpy(t,s,5);
    printf("sachin p is [%s], t is [%s]",p,t);
    return 0;
}

Output

sachin p is [sa], t is [sa]

what could be done to see this effect

Compile and run this code:

void dump5(char *str);

int main()
{
    char s[5]={'s','a','\0','c','h'};

    char membuff[5]; 
    char strbuff[5];
    memset(membuff, 0, 5); // init both buffers to nulls
    memset(strbuff, 0, 5);

    strcpy(strbuff,s);
    memcpy(membuff,s,5);

    dump5(membuff); // show what happened
    dump5(strbuff);

    return 0;
}

void dump5(char *str)
{
    char *p = str;
    for (int n = 0; n < 5; ++n)
    {
        printf("%2.2x ", *p);
        ++p;
    }

    printf("\t");

    p = str;
    for (int n = 0; n < 5; ++n)
    {
        printf("%c", *p ? *p : ' ');
        ++p;
    }

    printf("\n", str);
}

It will produce this output:

73 61 00 63 68  sa ch
73 61 00 00 00  sa

You can see that the "ch" was copied by memcpy(), but not strcpy().

strcpy stops when it encounters a NUL ('\0') character, memcpy does not. You do not see the effect here, as %s in printf also stops at NUL.

strcpy terminates when the source string's null terminator is found. memcpy requires a size parameter be passed. In the case you presented the printf statement is halting after the null terminator is found for both character arrays, however you will find t[3] and t[4] have copied data in them as well.

strcpy copies character from source to destination one by one until it find NULL or '\0' character in the source.

while((*dst++) = (*src++));

where as memcpy copies data (not character) from source to destination of given size n, irrespective of data in source.

memcpy should be used if you know well that source contain other than character. for encrypted data or binary data, memcpy is ideal way to go.

strcpy is deprecated, so use strncpy.