Is it possible to print out only a certain section of a C-string, without making a separate substring?
Is it possible to print out only the last 5 bytes of this string?
Yes, just pass a pointer to the fifth-to-the-last character. You can determine this by string + strlen(string) - 5
.
What about the first 5 bytes only?
Use a precision specifier: %.5s
#include <stdio.h>
#include <string.h>
char* string = "Hello, how are you?";
int main() {
/* print at most the first five characters (safe to use on short strings) */
printf("(%.5s)\n", string);
/* print last five characters (dangerous on short strings) */
printf("(%s)\n", string + strlen(string) - 5);
int n = 3;
/* print at most first three characters (safe) */
printf("(%.*s)\n", n, string);
/* print last three characters (dangerous on short strings) */
printf("(%s)\n", string + strlen(string) - n);
return 0;
}
Yes, the last five bytes of that string can be done with:
printf ("%s\n", &(string[strlen (string) - 5]));
The first five can be done with:
printf ("%.5s\n", string);
You can combine the two to get substrings within the string as well. The word how
can be printed with:
printf ("%.3s\n", &(string[strlen (string) + 7]));
You do have to be careful that the string is long enough for this to work. Printing the last five characters of a one-character string will cause undefined behaviour since the index ends up at -4
. In other words, check the string length before attempting this.