Tutorials

C Header Files

C Header Files

C Library – string.h

Posted in C Tutorial

Updated on Jun 02, 2024

By Mari Selvan

👁️ 24 - Views

⏳ 4 mins

💬 0

Photo Credit to CodeToFun

🙋 Introduction

The <string.h> header file in the C programming language provides a collection of functions for manipulating C strings and arrays of characters. These functions enable common operations like copying, concatenation, comparison, and searching within strings. Mastering <string.h> is essential for efficient string handling in C programs.

💡 Syntax

To use the functions provided by <string.h>, include the header file at the beginning of your C program:

example.c

Copied

#include <string.h>

📚 Key Functions and Macros

Here are some of the key functions and macros available in <string.h>:

strcpy():

Copies a string from a source to a destination.

example.c

Copied

char destination[20];
char source[] = "Hello, World!";
strcpy(destination, source);

strncpy():

Copies up to n characters from a source to a destination, ensuring no overflow.

example.c

Copied

char destination[20];
char source[] = "Hello, World!";
strncpy(destination, source, 5); // Copies "Hello"
destination[5] = '\0'; // Null-terminate the string

strcat():

Appends a source string to the end of a destination string.

example.c

Copied

char destination[20] = "Hello, ";
char source[] = "World!";
strcat(destination, source);

strncat():

Appends up to n characters from a source string to a destination string.

example.c

Copied

char destination[20] = "Hello, ";
char source[] = "World!";
strncat(destination, source, 5); // Appends "World"

strcmp():

Compares two strings lexicographically.

example.c

Copied

char str1[] = "Hello";
char str2[] = "World";
int result = strcmp(str1, str2); // result < 0 because "Hello" is less than "World"

strncmp():

Compares up to n characters of two strings.

example.c

Copied

char str1[] = "Hello";
char str2[] = "Help";
int result = strncmp(str1, str2, 3); // result = 0 because the first 3 characters are equal

strlen():

Returns the length of a string.

example.c

Copied

char str[] = "Hello, World!";
size_t length = strlen(str); // length = 13

strchr():

Finds the first occurrence of a character in a string.

example.c

Copied

char str[] = "Hello, World!";
char *ptr = strchr(str, 'W'); // ptr points to the first occurrence of 'W'

strstr():

Finds the first occurrence of a substring in a string.

example.c

Copied

char str[] = "Hello, World!";
char *ptr = strstr(str, "World"); // ptr points to the first occurrence of "World"

📝 Basic Example:

Here's a complete example demonstrating the use of several <string.h> functions to manipulate strings:

example.c

Copied

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

int main() {
  char str1[20] = "Hello, ";
  char str2[] = "World!";
  char str3[20];

  // Copying str2 to str3
  strcpy(str3, str2);
  printf("str3: %s\n", str3);

  // Concatenating str1 and str2
  strcat(str1, str2);
  printf("str1: %s\n", str1);

  // Finding the length of str1
  size_t length = strlen(str1);
  printf("Length of str1: %zu\n", length);

  // Comparing str2 and str3
  int result = strcmp(str2, str3);
  printf("strcmp result: %d\n", result);

  return 0;
}

💻 Output

Output

str1: Hello, World!
Length of str1: 13
strcmp result: 0

💰 Benefits

Using the <string.h> library offers several benefits:

Standardization: As part of the C standard library, <string.h> provides a consistent and portable way to handle string operations across different platforms and compilers.
Ease of Use: The functions in <string.h> are straightforward and well-documented, making string manipulation easier even for beginners.
Efficiency: The functions are optimized for performance, ensuring efficient string operations, which is crucial for applications that process large amounts of text.
Comprehensive Functionality: With a wide range of functions, <string.h> covers various aspects of string manipulation, from simple copying to complex searching and comparison.
Interoperability: The standardized functions facilitate interoperability with other libraries and systems that use similar string representations.

🎉 Conclusion

The <string.h> library in C is an indispensable tool for handling various string operations. By leveraging the functions it provides, you can perform complex string manipulations with ease and efficiency.

Understanding and utilizing <string.h> is crucial for developing robust and performant C programs.