String Functions

We learned that strings in C are arrays of char that end with '\0'. Working with them manually (character by character) is tedious. The string.h library gives us ready-made functions

#include <stdio.h>
#include <string.h>

int main(void) {
    char name[] = "Dennis Ritchie";
    printf("Length: %lu\n", strlen(name));
    return 0;
}

Output

Length: 14

strlen returns the number of characters in the string, NOT counting the '\0'. The actual array has 15 chars (14 letters + '\0'), but strlen says 14. This is an important distinction

strcmp: compare two strings

#include <stdio.h>
#include <string.h>

int main(void) {
    char a[] = "apple";
    char b[] = "banana";
    char c[] = "apple";

    printf("%d\n", strcmp(a, b));   // negative (a comes before b)
    printf("%d\n", strcmp(b, a));   // positive (b comes after a)
    printf("%d\n", strcmp(a, c));   // 0 (they're equal)
    return 0;
}

strcmp returns 0 if the strings are equal, a negative number if the first comes before the second (alphabetically), and a positive number if it comes after. Remember: in C, you cannot compare strings with ==. That compares addresses, not content

strcpy: copy one string into another

#include <stdio.h>
#include <string.h>

int main(void) {
    char source[] = "Hello";
    char dest[20];

    strcpy(dest, source);
    printf("%s\n", dest);   // Hello
    return 0;
}

strcpy(dest, source) copies everything from source into dest, including the '\0'. Make sure dest is big enough! If it's too small, you get a buffer overflow, one of the most dangerous bugs in programming. This is how real security vulnerabilities happen

strcat: concatenate (join) two strings

#include <stdio.h>
#include <string.h>

int main(void) {
    char greeting[50] = "Hello, ";
    strcat(greeting, "teletype!");
    printf("%s\n", greeting);   // Hello, teletype!
    return 0;
}

strcat appends the second string to the end of the first. Again, make sure the destination array is big enough for both strings plus the '\0'

A useful trick: strstr (find a substring)

#include <stdio.h>
#include <string.h>

int main(void) {
    char text[] = "I love programming in C";
    char *found = strstr(text, "programming");

    if (found != NULL) {
        printf("Found: %s\n", found);   // Found: programming in C
    }
    return 0;
}

strstr returns a pointer to where the substring starts, or NULL if it's not found. NULL is C's way of saying "nothing": it's a special pointer value that means "points to nothing." We'll see it a lot

Mission: Assembling the Tape Label

An old magnetic tape has lost its label. Two different operators each transcribed half of it, on separate teletypes. Your job: measure the first fragment, then join both fragments into a single string and print the full label.

1. Read two words from input, first and second (no internal spaces)
2. Print the length of first (use strlen)
3. Copy first into an array result (use strcpy, make result big enough: char result[50])
4. Concatenate second onto result (use strcat)
5. Print result

Example

Input

Bell Labs

Output

4
BellLabs

Example

Input

Tele type

Output

4
Teletype