# Common String Functions

C programming provides a set of standard library functions for manipulating strings. These functions are declared in the `<string.h>` header file and offer various operations to work with character arrays. Let's explore some common string functions and their usage.

## 1. `strlen` - String Length

```c
#include <string.h>

size_t strlen(const char *str);
```

This function returns the length of the input string, excluding the null character. It calculates the number of characters in the string.

```c
const char *message = "Hello, World!";
size_t length = strlen(message); // Returns 13
```

## 2. `strcpy` - String Copy

```c
#include <string.h>

char *strcpy(char *dest, const char *src);
```

This function copies the contents of the source string (`src`) to the destination string (`dest`). It includes the null character in the copied sequence.

```c
char source[] = "Copy me!";
char destination[20];
strcpy(destination, source); // destination now contains "Copy me!"
```

## 3. `strcat` - String Concatenate

```c
#include <string.h>

char *strcat(char *dest, const char *src);
```

This function appends the contents of the source string (`src`) to the destination string (`dest`). The destination string must have enough space to accommodate both strings.

```c
char greeting[20] = "Hello";
strcat(greeting, ", World!"); // greeting now contains "Hello, World!"
```

## 4. `strcmp` - String Compare

```c
#include <string.h>

int strcmp(const char *str1, const char *str2);
```

This function compares two strings (`str1` and `str2`) lexicographically. It returns an integer less than, equal to, or greater than zero, indicating whether the first string is less than, equal to, or greater than the second string.

```c
const char *string1 = "apple";
const char *string2 = "banana";
int result = strcmp(string1, string2); // Returns a value < 0
```

## 5. `strncpy` - String Copy with Length Limit

```c
#include <string.h>

char *strncpy(char *dest, const char *src, size_t n);
```

This function copies at most `n` characters from the source string (`src`) to the destination string (`dest`). It ensures that the destination is null-terminated if `n` is sufficient.

```c
char source[] = "Copy me!";
char destination[5];
strncpy(destination, source, 4); // destination now contains "Copy"
```

These are just a few examples of the many string functions available in C. Understanding and using these functions appropriately will enhance your ability to work with strings in C programming.

If you have specific questions or if there are additional topics you'd like to explore, feel free to ask!