String

字符串

字符串基础

字符串常量（字符串字面量）

• char array[] = "Hello, World!";

• array是字符串变量

• 右边的"Hello, World!"是字符串常量

字符串：是以'\0'为结尾的 char 数组。未被初始化的富裕内存也被初始化为\0

#include <stdio.h>
int main()
{
    char array1[8] = "Hello";
    char array2[8] = "Hello\0\0\0";
    for (int i = 0; i < 8; i++) // 11111111
        printf("%d", array1[i] == array2[i]);
    return 0;
}

字符串数组不能递增，而指向字符串的指针可以

#include <stdio.h>
#include <string.h>
int main()
{
    char array1[] = "Hello";
    char *array2 = "World";
    for (int i = 0; i < strlen(array1); i++)
        printf("%c", array1[i]); // Hello
    for (int i = 0; i < strlen(array2); i++)
        printf("%c", array2[i]); // World
    // for (int i = 0; i < strlen(array1); i++)
    //     printf("%c", *array1++); // Wrong!!
    for (int i = 0; i < strlen(array2); i++)
        printf("%c", *array2++); // World
    return 0;
}

字符串数组：const char *mytalents[LIM]

//  arrchar.c -- array of pointers, array of strings
#include <stdio.h>
#define SLEN 40
#define LIM 5
int main(void)
{
    // const char(*mytalents)[LIM]
    const char *mytalents[LIM] = {
        "Adding numbers swiftly",
        "Multiplying accurately", "Stashing data",
        "Following instructions to the letter",
        "Understanding the C language"};
    char yourtalents[LIM][SLEN] = {
        "Walking in a straight line",
        "Sleeping", "Watching television",
        "Mailing letters", "Reading email"};
    int i;

    puts("Let's compare talents.");
    printf("%-36s  %-25s\n", "My Talents", "Your Talents");
    for (i = 0; i < LIM; i++)
        printf("%-36s  %-25s\n", mytalents[i], yourtalents[i]);
    printf("\nsizeof mytalents: %zd, sizeof yourtalents: %zd\n",
           sizeof(mytalents), sizeof(yourtalents));

    return 0;
}

字符串相关的库

详见：stdio.h

• 输入

  • printf()

  • gets()：读取整行（包括空格），不检查字符串长度。不要用

  • fgets()：推荐用

  • gets_s()：C11 的新函数，编译器大概率不支持

• 输出

  • scanf

  • puts：会自动换行

  • fputs：不会自动换行

• 格式化

  • sprintf()

详见：string.h

• strlen()

• strcat(), strncat()

• strcmp(), strncmp()

• strcpy(), strncpy()