What is string function in C ?

In C programming, string functions are a set of built-in functions that operate on character arrays (strings) and provide various operations for manipulating and working with strings. These functions are included in the standard C library header file <string.h>. String functions are used to perform common string operations such as copying, concatenating, comparing, searching, and manipulating strings.

Here is a table explaining some commonly used string functions in C:

1. strlen(string)

Examples:

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

int main() {
    char str[] = "Hello, World!";
    int length = strlen(str);
    printf("Length of the string: %d\n", length);
    return 0;
}

Output:

Length of the string: 13

Explanation:

This example demonstrates the usage of strlen function to find the length of a string. The function strlen returns an integer representing the length of the provided string excluding the null character.

2. strcpy(destination, source)

Examples:

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

int main() {
    char source[] = "Hello, World!";
    char destination[20];
    strcpy(destination, source);
    printf("Copied string: %s\n", destination);
    return 0;
}

Output:

Copied string: Hello, World!

Explanation:

This example shows how to use strcpy to copy a string from the source to the destination. The strcpy function copies the contents of the source string to the destination string.

3. strncpy(destination, source, n)

Examples:

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

int main() {
    char source[] = "Hello, World!";
    char destination[10];
    strncpy(destination, source, 5);
    destination[5] = '\0';
    printf("Copied string: %s\n", destination);
    return 0;
}

Output:

Copied string: Hello

Explanation:

This example demonstrates the usage of strncpy function to copy a certain number of characters (5 characters in this case) from the source to the destination. The strncpy function copies the specified number of characters or until it reaches the null character, whichever comes first. It is important to manually append the null character to ensure the resulting string is properly terminated.

4. strcat(destination, source)

Examples:

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

int main() {
    char destination[20] = "Hello";
    char source[] = ", World!";
    strcat(destination, source);
    printf("Concatenated string: %s\n", destination);
    return 0;
}

Output:

Concatenated string: Hello, World!

Explanation:

This example shows how to use strcat to concatenate (append) one string to the end of another. The strcat function appends the source string to the destination string.

5. strncat(destination, source, n)

Examples:

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

int main() {
    char destination[20] = "Hello";
    char source[] = ", World!";
    strncat(destination, source, 5);
    printf("Concatenated string: %s\n", destination);
    return 0;
}

Output:

Concatenated string: Hello, Wor

Explanation:

This example demonstrates the usage of strncat function to concatenate a certain number of characters (5 characters in this case) from the source to the end of the destination. The strncat function appends the specified number of characters from the source string to the destination string or until it reaches the null character, whichever comes first.

6. strcmp(string1, string2)

Examples:

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

int main() {
    char str1[] = "Hello";
    char str2[] = "World";
    int result = strcmp(str1, str2);
    if (result == 0) {
        printf("Strings are equal\n");
    } else if (result < 0) {
        printf("String 1 is less than String 2\n");
    } else {
        printf("String 1 is greater than String 2\n");
    }
    return 0;
}

Output:

String 1 is less than String 2

Explanation:

This example showcases the usage of strcmp function to compare two strings. The strcmp function returns an integer value indicating the relation between the strings: 0 if both strings are equal, a negative value if the first string is less than the second, or a positive value if the first string is greater than the second.

7. strncmp(string1, string2, n)

Examples:

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

int main() {
    char str1[] = "Hello";
    char str2[] = "Help";
    int result = strncmp(str1, str2, 3);
    if (result == 0) {
        printf("Strings are equal\n");
    } else if (result < 0) {
        printf("String 1 is less than String 2\n");
    } else {
        printf("String 1 is greater than String 2\n");
    }
    return 0;
}

Output:

Strings are equal

Explanation:

This example demonstrates the usage of strncmp function to compare a certain number of characters (3 characters in this case) of two strings. The strncmp function returns an integer value indicating the relation between the strings, similar to strcmp.

8. strchr(string, c)

Examples:

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

int main() {
    char str[] = "Hello, World!";
    char *ptr = strchr(str, 'W');
    printf("Character found: %c\n", *ptr);
    return 0;
}

Output:

Character found: W

Explanation:

This example showcases the usage of strchr function to search for the first occurrence of a character in a string. The strchr function returns a pointer to the first occurrence of the specified character in the string or NULL if the character is not found.

9. strrchr(string, c)

Examples:

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

int main() {
    char str[] = "Hello, World!";
    char *ptr = strrchr(str, 'o');
    printf("Character found: %c\n", *ptr);
    return 0;
}

Output:

Character found: o

Explanation:

This example demonstrates the usage of strrchr function to search for the last occurrence of a character in a string. The strrchr function returns a pointer to the last occurrence of the specified character in the string or NULL if the character is not found.

10 strstr(string1, string2)

Examples:

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

int main() {
    char str1[] = "Hello, World!";
    char str2[] = "World";
    char *ptr = strstr(str1, str2);
    printf("Substring found: %s\n", ptr);
    return 0;
}

Output:

Substring found: World!

Explanation:

This example showcases the usage of strstr function to search for the first occurrence of a substring in a string. The strstr function returns a pointer to the first occurrence of the specified substring in the string or NULL if the substring is not found.

11. strtok(string, delimiter)

Examples:

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

int main() {
    char str[] = "Hello,World,How,Are,You";
    char *token = strtok(str, ",");
    while (token != NULL) {
        printf("%s\n", token);
        token = strtok(NULL, ",");
    }
    return 0;
}

Output:

Hello
World
How
Are
You

Explanation:

This example demonstrates the usage of strtok function to break a string into a series of tokens based on a delimiter. The strtok function returns a pointer to the next token found in the string or NULL if there are no more tokens.

12. sprintf(string, format, …)

Examples:

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

int main() {
    char str[20];
    int number = 42;
    sprintf(str, "The answer is %d", number);
    printf("%s\n", str);
    return 0;
}

Output:

The answer is 42

Explanation:

This example shows how to use sprintf function to write formatted data to a string. The sprintf function formats the data according to the specified format string and stores it in the provided string.

13. sscanf(string, format, …)

Examples:

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

int main() {
    char str[] = "John Doe 25";
    char name[20];
    int age;
    sscanf(str, "%s %s %d", name, name, &age);
    printf("Name: %s\n", name);
    printf("Age: %d\n", age);
    return 0;
}

Output:

Name: Doe
Age: 25

Explanation:

This example demonstrates the usage of sscanf function to read formatted data from a string. The sscanf function scans the input string according to the specified format string and stores the extracted values in the provided variables.

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