YouTipC Strings
# C Strings
In the C language, a string is actually a one-dimensional character array terminated by the null character . Therefore, is used to mark the end of a string.
**Null character** (also known as the terminator, abbreviated NUL) is a control character with a numeric value of 0. is an escape character, which tells the compiler that this is not the character 0, but the null character.
The following declaration and initialization creates a **** string. Since the null character is stored at the end of the array, the size of the character array is one more than the number of characters in the word ****.
```c
char site = {'R', 'U', 'N', 'O', 'O', 'B', ''};
According to array initialization rules, you can write the above statement as:
```c
char site[] = "";
The following is the memory representation of a string defined in C/C++:
Actually, you don't need to place the null character at the end of a string constant. The C compiler automatically places at the end of the string when initializing the array. Let's try to output the string above:
## Example
```c
#include
int main()
{
char site = {'R', 'U', 'N', 'O', 'O', 'B', ''};
printf(": %sn", site);
return 0;
}
When the above code is compiled and executed, it produces the following result:
:
There are a large number of functions for manipulating strings in C:
| No. | Function & Purpose |
| --- | --- |
| 1 | **strcpy(s1, s2);** Copies string s2 into string s1. |
| 2 | **strcat(s1, s2);** Concatenates string s2 to the end of string s1. |
| 3 | **strlen(s1);** Returns the length of string s1. |
| 4 | **strcmp(s1, s2);** Returns 0 if s1 and s2 are the same; less than 0 if s1s2. |
| 5 | **strchr(s1, ch);** Returns a pointer to the first occurrence of character ch in string s1. |
| 6 | **strstr(s1, s2);** Returns a pointer to the first occurrence of string s2 in string s1. |
The following example uses some of the above functions:
## Example
```c
#include
#include
int main()
{
char str1 = "";
char str2 = "google";
char str3;
int len ;
/* Copy str1 to str3 */
strcpy(str3, str1);
printf("strcpy( str3, str1) : %sn", str3);
/* Concatenate str1 and str2 */
strcat(str1, str2);
printf("strcat( str1, str2): %sn", str1);
/* Total length after concatenation */
len = strlen(str1);
printf("strlen(str1) : %dn", len);
return 0;
}
When the above code is compiled and executed, it produces the following result:
strcpy( str3, str1) :
strcat( str1, str2): tutorialgoogle
strlen(str1) : 12
You can find more string-related functions in the C Standard Library.
## 7 Notes Write a Note
1. #0 San San
mr.***ogyo@outlook.com 457 Functions covered in this section and their full English names
strcmp: string compare
strcat: string catenate
strcpy: string copy
strlen: string length
strlwr: string lowercase
strupr: string uppercase
(javascript:;)San San
mr.***ogyo@outlook.com 9 years ago (2017-11-06)
2. #0 Felix
pho***xdai@foxmail.com 128 When initializing a string with the following input, special attention must be paid to :
```c
char greeting = {'H', 'e', 'l', 'l', 'o', ''};
If is not added at the end of the character array, the output will be incorrect:
```c
// Initialize string
char greeting = { 'H', 'e', 'l', 'l', 'o' };
printf("Greeting message: %sn", greeting);
Output:
Greeting message: HelloUninitialized Memory?Intrusion7(?╔?╚╔╔
When using a variable-length array to initialize a string, the default ending is
```c
char greeting[] = "Hello";
printf("Greeting message: %s, greeting[] Length: %dn", greeting, sizeof(greeting));
Output:
Greeting message: Hello, greeting[] Length: 6
**Conclusion:** When specifying the size of a character array, add 1 to the number of characters in the original string.
(javascript:;)Felix
pho***xdai@foxmail.com 8 years ago (2018-07-11)
3. #0 Wang Ning Cao~~~
tom***owww13@163.com
(#) 115
**Difference between strlen and sizeof:**
strlen is a function, sizeof is an operator. Both return results of type size_t, i.e., unsigned int type.
- sizeof calculates the size of a variable and is not affected by the character ;
- strlen calculates the length of a string, using as the basis for length determination.
> More reference content:
>
>
> > [Wang Ning Cao~~~](javascript:;)
Wang Ning Cao~~~
tom***owww13@163.com
(#)
8 years ago (2018-07-30)
4. #0 Beginner Also Famous
277***4352@qq.com
(https://bbs.csdn.net/topics/20311409