C String Functions

Welcome to The Coding College, your trusted resource for mastering programming concepts. In this tutorial, we will explore string functions in C, their applications, and examples to help you manipulate strings effectively.

String functions are essential tools for handling and manipulating strings in C, making them a cornerstone of programming for tasks like text formatting, validation, and data processing.

What Are String Functions in C?

C uses the <string.h> library to provide a collection of built-in functions for string manipulation. These functions allow you to perform operations like:

  • Calculating the length of a string.
  • Copying one string to another.
  • Comparing two strings.
  • Concatenating (joining) strings.
  • Searching for substrings or characters.

Commonly Used String Functions in C

Here’s a list of commonly used string functions, their purposes, and examples:

FunctionDescriptionExample
strlen()Finds the length of a string.strlen("Hello") returns 5.
strcpy()Copies one string to another.strcpy(dest, source);
strncpy()Copies specified characters from one string to another.strncpy(dest, source, n);
strcat()Concatenates two strings.strcat(str1, str2);
strncat()Concatenates a specified number of characters.strncat(str1, str2, n);
strcmp()Compares two strings.strcmp("abc", "abc") returns 0.
strncmp()Compares specified characters of two strings.strncmp(str1, str2, n);
strchr()Finds the first occurrence of a character.strchr("hello", 'e') returns pointer to e.
strrchr()Finds the last occurrence of a character.strrchr("hello", 'l') returns pointer to l.
strstr()Finds a substring in a string.strstr("programming", "gram").
strtok()Splits a string into tokens.strtok(str, delim);

Examples of String Functions

Example 1: Finding String Length with strlen()

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

int main() {
    char str[] = "The Coding College";
    printf("Length of string: %zu\n", strlen(str));
    return 0;
}

Output:

Length of string: 18

Example 2: Copying Strings with strcpy()

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

int main() {
    char source[] = "Hello, World!";
    char destination[50];
    strcpy(destination, source);
    printf("Copied String: %s\n", destination);
    return 0;
}

Output:

Copied String: Hello, World!

Example 3: Comparing Strings with strcmp()

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

int main() {
    char str1[] = "Apple";
    char str2[] = "Banana";

    if (strcmp(str1, str2) == 0) {
        printf("Strings are equal.\n");
    } else {
        printf("Strings are not equal.\n");
    }

    return 0;
}

Output:

Strings are not equal.

Example 4: Concatenating Strings with strcat()

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

int main() {
    char str1[50] = "Welcome to ";
    char str2[] = "The Coding College";

    strcat(str1, str2);
    printf("%s\n", str1);
    return 0;
}

Output:

Welcome to The Coding College

Example 5: Splitting a String with strtok()

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

int main() {
    char str[] = "C,Programming,Made,Easy";
    char *token = strtok(str, ",");

    while (token != NULL) {
        printf("%s\n", token);
        token = strtok(NULL, ",");
    }

    return 0;
}

Output:

C
Programming
Made
Easy

Practical Applications of String Functions

  1. User Input Handling
    Validate and process user inputs like names, passwords, or commands.
  2. File Parsing
    Extract specific data from files, such as CSV or JSON formats.
  3. Search and Replace
    Locate substrings and replace them with new values.
  4. Tokenization
    Split complex strings into manageable parts, such as parsing URLs or commands.

Best Practices for Using String Functions

  1. Check String Length
    Ensure the destination string has sufficient space before copying or concatenating.
  2. Use Safe Functions
    Prefer strncpy() and strncat() over strcpy() and strcat() to avoid buffer overflows.
  3. Null Termination
    Always ensure strings are properly null-terminated to prevent undefined behavior.
  4. Avoid Overuse of strtok()
    Use alternatives when working with multi-threaded environments, as strtok() is not thread-safe.

Conclusion

String functions are indispensable tools for C programmers. Mastering them enables efficient manipulation of text, improving your ability to create robust and scalable applications.

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