CODEWITHSUNDEEP
cstring
Kevin Mogi
Kevin Mogi

Reputation: 117

string relation with '\0'

as far as i know, that every string always terminated with '\0',

so my question is

int main()
{   
    char string1[6]="hello";
   // char string2[5]="hello"; // doesnt work

    printf("%d",strlen(string));

    getchar();
    getchar();
    return 0;
}
  1. why when i check the length of string1, it shows 5 not 6,which is mean that '\0' doesn't in count, but the array itself count '\0', only allow us to declare at least string[6] not string[5]? is there any further explanation about this?
  2. is there any special case that we are able to end string without '\0'?

Upvotes: 2

Views: 411

Answers (3)

skearney
skearney

Reputation: 126

Yes, the C language uses '\0' as a sentinel character to find the end of a string. strlen() returns the length of the string excluding the null character.

You can automatically create a char[] array of the proper size to hold your string constant (including the null character) by omitting the number inside the brackets:

char string1[] = "hello";

printf("%d", strlen(string1)); // prints 5

This way you can avoid confusion regarding the array length.

To answer question 2: Not if you still want to treat it as a string (i.e. still use the functions in <string.h> to manipulate it).

Upvotes: 1

R Sahu
R Sahu

Reputation: 206567

Use of the terminating null character allows a program to determine where a string ends. If you didn't have the null terminator, you can determine the length of a string either using a different string terminating character or store the length of the string in the string. Using '\0' for the terminating null character is most likely historical. That's my guess.

As far as

is there any special case that we are able to end string without '\0'?

No. All of the C library functions that work with strings expect the '\0'. Otherwise, they won't be able to determine which element of an array to stop at. As a consequence, they will end up accessing memory out of bounds.

You can create an array of characters that don't have a terminating null character but that won't be a string.

char arr[2] = {'a', 'b'};

is perfectly fine. You can access arr[0] and arr[1] without any problem. However, you can't use arr as an argument to strlen. Doing that will lead to undefined behavior.

Upvotes: 2

John Zwinck
John Zwinck

Reputation: 249123

C style strings are traditionally stored with a null terminator. Functions like strlen() do not count this null terminator, and give you the "human" length of the string, e.g. "hello" is length 5.

However, you are welcome to store strings without the null terminator if you want; some systems use strings with length prefixes instead, for example, or use strings of fixed capacity with space padding, or other schemes. C doesn't prevent you from doing these things, but if you do, you won't be able to use functions like strlen() anymore.

Upvotes: 4

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