Strings in C Programming Language

Strings in C Programming Language: Strings in C are fundamental to managing text data. By using arrays of characters and a variety of string manipulation functions, C allows efficient string handling. Understanding both built-in functions and manual operations can make your code versatile and efficient.

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What is Strings in C Programming Language

In C programming, a string is essentially a collection of characters stored in a contiguous memory location, terminated by a null character (\0). Strings are arrays of characters but treated differently for various operations.

Declaration of Strings in C Programming Language

In C, strings are declared as arrays of characters. You can declare a string in two ways:

Using character arrays:

char str[10] = “Hello”;

Here, str can store up to 9 characters, plus the null terminator (\0).

Using string literals:

char *str = “Hello”;

This creates a pointer to a string literal.

Null Terminator (\0)

C strings are always terminated by a special character called the null terminator, represented as \0. This signifies the end of the string and allows functions to determine where the string ends.

Input and Output of Strings in C Programming Language

Reading a String

You can read a string from the user using scanf or gets functions.

Using scanf:

char str[100];
scanf(“%s”, str);
The problem with scanf is that it stops reading input when it encounters a whitespace character (space, tab, newline).

Using gets:

char str[100];
gets(str);
gets reads the entire line, including spaces, but is unsafe as it doesn’t check buffer overflow.

Using fgets (Safe way):

char str[100];
fgets(str, 100, stdin);
fgets allows you to specify the maximum number of characters to read and is a safer alternative.

Printing a String

You can print a string using the printf function.

printf(“%s”, str);

Functions Strings in C Programming Language

C provides a set of built-in functions for performing various string operations. These functions are declared in the string.h header file.

strlen() – Find the length of a string:

int length = strlen(str);
This function returns the number of characters in the string, excluding the null terminator.

strcpy() – Copy one string into another:

strcpy(destination, source);
This function copies the content of the source string into the destination.

strcat() – Concatenate two strings:

strcat(destination, source);
This function appends the source string to the destination string.

strcmp() – Compare two strings:

int result = strcmp(str1, str2);
This function compares two strings. If the strings are equal, it returns 0. If str1 is greater than str2, it returns a positive value, and if str1 is less than str2, it returns a negative value.

strncpy() – Copy a specified number of characters:

strncpy(destination, source, n);
This function copies n characters from the source string to the destination string.

strncat() – Concatenate a specified number of characters:

strncat(destination, source, n);
This function appends n characters from the source string to the destination string.

strchr() – Find the first occurrence of a character:

char *ptr = strchr(str, ‘a’);
This function returns a pointer to the first occurrence of the character a in the string.

strstr() – Find a substring within a string:

char *ptr = strstr(str, “world”);
This function returns a pointer to the first occurrence of the substring “world” in str.

String Manipulation Without Built-in Functions Strings in C Programming Language

You can also perform string operations manually without using built-in functions. For example, to find the length of a string:

int string_length(char str[]) {
int i = 0;
while (str[i] != ‘\0’) {
i++;
}
return i;
}

Example Program: Basic String Operations

#include<stdio.h>

#include<string.h>

int main() {
char str1[100], str2[100];

// Input strings
printf("Enter first string: ");
gets(str1);
printf("Enter second string: ");
gets(str2);

// String length
printf("Length of first string: %lu\n", strlen(str1));

// String copy
strcpy(str2, str1);
printf("After copying, second string: %s\n", str2);

// String concatenation
strcat(str1, str2);
printf("After concatenation: %s\n", str1);

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

return 0;

}

Memory Allocation for Strings in C

In C, when handling dynamic strings, you can use pointers with memory allocation functions like malloc and free from the stdlib.h library.

Example:

#include<stdio.h>

#include<string.h>

int main() {
char *str;

// Allocate memory for string
str = (char *)malloc(100 * sizeof(char));
if (str == NULL) {
    printf("Memory allocation failed\n");
    return 1;
}

// Input and output
printf("Enter a string: ");
gets(str);
printf("You entered: %s\n", str);

// Free allocated memory
free(str);

return 0;

}

String and Character Pointers in C

In C, a string can also be manipulated using a pointer to a character. For instance, you can traverse a string using a pointer.

Example:

#include<stdio.h>

int main() {
char str[] = “Hello”;
char *ptr = str;

// Traverse string using pointer
while (*ptr != '\0') {
    printf("%c", *ptr);
    ptr++;
}

return 0;

}

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