Usage of string in c language

Strings in the C language are stored as null-terminated character arrays. Its characters can be accessed via subscripts, using strlen() to find the length. String operations include input/output, comparison, copying, concatenation, and searching. The sample code demonstrates operations such as access, length, copy, and search.

String in C language

In C language, a string is a null-terminated character array.

Use of string

• Declare string: char str[] = "Hello World";
• Access string characters: str[i], where i is the index of the character in the string.
• String length: Use the strlen() function.

String operations

Input and output:

• Input string: gets() or scanf()
• Output string: puts() or printf()

Comparison:

• String equality: strcmp(str1, str2) == 0
• Strings are not equal: strcmp(str1, str2) != 0

##Copy:

• Copy string: strcpy(destination, source)
• Safe copy: strncpy(destination, source, n)

Splicing:

• String splicing: strcat(str1, str2)

Search:

• The position where the character appears in the string: strchr(str, ch)
• The position where the substring appears in the string: strstr(str, sub)

Example

<code class="c">#include <stdio.h>
#include <string.h>

int main() {
    char str[] = "Hello World";

    // 访问字符串字符
    printf("第一个字符：%c\n", str[0]);

    // 字符串长度
    printf("字符串长度：%d\n", strlen(str));

    // 字符串比较
    if (strcmp(str, "Hello World") == 0) {
        printf("字符串相等\n");
    }

    // 字符串复制
    char copy[20];
    strcpy(copy, str);

    // 字符串拼接
    strcat(str, "! Welcome");

    // 字符串搜索
    char* pos = strchr(str, '!');
    if (pos) {
        printf("感叹号的位置：%d\n", pos - str);
    }

    return 0;
}</code>

Output:

<code>第一个字符：H
字符串长度：11
字符串相等
Hello World! Welcome
感叹号的位置：11</code>

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