String built-in functions in C

String manipulation is a common task in C programming. Fortunately, C provides a set of built-in functions specifically designed to handle strings. These functions simplify string operations and allow programmers to efficiently work with textual data. In this article, we will explore various string built-in functions in C, their usage, and practical examples.

The <string.h> Library

The <string.h> library in C contains several useful functions for string manipulation. It is essential to include this library at the beginning of your program to access the string functions.

Commonly Used String Functions

Let’s dive into some of the commonly used string built-in functions in C:

1. strlen():

  • Purpose: Determines the length of a string.
  • Syntax: size_t strlen(const char *str);
  • Example:
char str[] = "Hello";
size_t length = strlen(str);
printf("Length: %zu\n", length);   // Output: 5

2. strcpy():

  • Purpose: Copies the contents of one string into another.
  • Syntax: char *strcpy(char *dest, const char *src);
  • Example:
char src[] = "Hello";
char dest[10];
strcpy(dest, src);
printf("Copied String: %s\n", dest);   // Output: "Hello"

3. strcat():

  • Purpose: Concatenates (appends) one string to the end of another.
  • Syntax: char *strcat(char *dest, const char *src);
  • Example:
char str1[] = "Hello";
char str2[] = " World";
strcat(str1, str2);
printf("Concatenated String: %s\n", str1);   // Output: "Hello World"

4. strcmp():

  • Purpose: Compares two strings and returns an integer based on the comparison result.
  • Syntax: int strcmp(const char *str1, const char *str2);
  • Example:
char str1[] = "Hello";
char str2[] = "World";
int result = strcmp(str1, str2);
if (result < 0)
    printf("str1 is less than str2\n");
else if (result > 0)
    printf("str1 is greater than str2\n");
    printf("str1 is equal to str2\n");

5. strchr():

  • Purpose: Searches for the first occurrence of a character in a string.
  • Syntax: char *strchr(const char *str, int c);
  • Example:
char str[] = "Hello";
char *ptr = strchr(str, 'l');
printf("Character found at position: %ld\n", ptr - str);   // Output: 2

Best Practices and Considerations

When using string built-in functions in C, it’s crucial to keep the following best practices in mind:

1. Buffer Overflow Prevention:

  • Ensure that the destination string has enough memory allocated to accommodate the result of string manipulation operations.
  • Use functions like strncpy() and strncat() to limit the number of characters copied or appended.

2. String Termination:

  • Always ensure that the resulting string is null-terminated to avoid undefined behavior.
  • Allocate sufficient memory for the destination string to accommodate the null character.


String built-in functions in C are powerful tools that simplify string manipulation tasks. They provide efficient ways to determine string length, copy strings, concatenate strings, compare strings, and search for characters. By utilizing these functions effectively, C programmers can handle strings with ease and create robust and efficient applications. Remember to follow best practices to ensure the integrity and stability of your code.