Convert a Character Array into a String in C

In C, a character array can be converted into a string by ensuring it is null-terminated or by using standard library functions like strcpy() or sprintf().

Strings in C are represented as arrays of characters ending with a null character '\0'.

In this tutorial, we cover different ways to convert a character array into a string.

Examples of Converting a Character Array into a String

1. Adding a Null Terminator Manually

In this example, we will manually add a null terminator ('\0') at the end of a character array to make it a valid C string.

main.c

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#include <stdio.h>

int main() {
    char charArray[6] = {'H', 'e', 'l', 'l', 'o', '\0'};

    printf("String: %s\n", charArray);
    
    return 0;
}

Explanation:

  1. We declare a character array charArray with 6 elements, including the null terminator '\0'.
  2. The null terminator explicitly marks the end of the string, making it a valid C string.
  3. The printf() function prints the character array as a string.

Output:

String: Hello

2. Using strcpy() to Copy a Character Array

In this example, we will use the strcpy() function from the string.h library to copy a character array into a string.

main.c

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

int main() {
    char charArray[] = {'W', 'o', 'r', 'l', 'd', '\0'};
    char string[10];

    strcpy(string, charArray); // Copy charArray to string

    printf("String: %s\n", string);
    
    return 0;
}

Explanation:

  1. We declare a character array charArray and ensure it ends with '\0'.
  2. We declare another character array string with enough space to store the copied characters.
  3. We use strcpy() to copy charArray into string, making it a valid string.
  4. The printf() function prints the converted string.

Output:

String: World

3. Using sprintf() for Conversion

In this example, we will use sprintf() to format a character array into a string.

main.c

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#include <stdio.h>

int main() {
    char charArray[] = "C Programming"; // Implicitly null-terminated
    char string[20];

    sprintf(string, "%s", charArray); // Format the character array into a string

    printf("String: %s\n", string);
    
    return 0;
}

Explanation:

  1. The character array charArray is initialized as a string, which means it already includes the '\0' terminator.
  2. We declare a character array string with enough space to store the formatted text.
  3. sprintf() copies the contents of charArray into string using formatted output.
  4. The printf() function prints the resulting string.

Output:

String: C Programming

Conclusion

In this tutorial, we covered different ways to convert a character array into a string in C:

  1. Manually adding a null terminator: Ensuring the character array ends with '\0' makes it a string.
  2. Using strcpy(): The standard string.h function copies a character array into another, converting it into a string.
  3. Using sprintf(): This function formats and stores characters into a string.

Each method is useful depending on the scenario, but ensuring the presence of a null terminator is key to proper string handling in C.