C语言函数大全--m 开头的函数（上）

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

int main()
{
    char *str = NULL;

    // 分配内存
    str = (char *)malloc(20 * sizeof(char));

    if (str == NULL)
    {
        printf("Failed to allocate memory.\n");
        return 1;
    }

    // 将字符串复制到内存中
    strcpy(str, "Hello, world!");

    // 输出字符串
    printf("%s\n", str);

    // 释放内存
    free(str);

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>

int main()
{
    // 设置本地化环境
    setlocale(LC_ALL, "");

    char str[] = u8"你好，世界！";
    int len;

    // 检查第一个字符的长度
    len = mblen(str, MB_CUR_MAX);

    if (len == -1)
    {
        printf("Failed to determine the length of the multibyte character.\n");
        return 1;
    }

    printf("The length of the first multibyte character is %d bytes.\n", len);

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <wchar.h>
#include <locale.h>

int main()
{
    // 设置本地化环境
    setlocale(LC_ALL, "");

    char str[] = u8"你好，世界！";
    int len;

    // 检查第一个字符的长度
    len = mbrlen(str, MB_CUR_MAX, NULL);

    if (len == (size_t)-2) // 特殊的返回值，表示发生了错误
    {
        printf("Failed to determine the length of the multibyte character.\n");
        return 1;
    }

    printf("The length of the first multibyte character is %d bytes.\n", len);

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <wchar.h>

int main()
{
    // 设置本地化环境
    setlocale(LC_ALL, "");

    char str[] = u8"你好，世界！";
    wchar_t wc;
    mbstate_t state = {0};

    // 将第一个字符转换为宽字符
    size_t len = mbrtowc(&wc, str, MB_CUR_MAX, &state);

    if (len == (size_t)-1)
    {
        printf("Failed to convert multibyte character.\n");
        return 1;
    }

    // 输出宽字符
    wprintf(L"The first wide character is: %lc\n", wc);

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <wchar.h>

int main()
{
    // 设置本地化环境
    setlocale(LC_ALL, "");

    char str[] = u8"你好，世界！";
    mbstate_t state = {0};

    // 检查转换状态是否为起始状态
    if (!mbsinit(&state))
    {
        printf("The conversion state is not initial.\n");
        return 1;
    }

    // 打印转换状态
    printf("The conversion state is %s.\n", (mbsinit(&state) ? "initial" : "not initial"));

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <wchar.h>

int main()
{
    // 设置本地化环境
    setlocale(LC_ALL, "");

    char str[] = u8"你好，世界！";
    wchar_t wcbuf[20];

    // 将多字节字符序列转换为宽字符序列
    size_t ret = mbstowcs(wcbuf, str, sizeof(wcbuf)/sizeof(wchar_t));

    if (ret == (size_t)-1)
    {
        printf("Failed to convert multibyte character sequence.\n");
        return 1;
    }

    // 在控制台输出宽字符序列及其长度
    wprintf(L"The wide character string is: %ls (%zu characters)\n", wcbuf, ret);

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <wchar.h>

int main()
{
    // 设置本地化环境
    setlocale(LC_ALL, "");

    char str[] = u8"你好，世界！";
    wchar_t wcbuf[20];
    mbstate_t state = {0};

    // 将多字节字符序列转换为宽字符序列
    size_t ret = mbsrtowcs(wcbuf, (const char**)&str, sizeof(wcbuf)/sizeof(wchar_t), &state);
    if (ret == (size_t)-1)
    {
        printf("Failed to convert multibyte character sequence.\n");
        return 1;
    }

    // 在控制台输出宽字符序列及其长度
    wprintf(L"The wide character string is: %ls (%zu characters)\n", wcbuf, ret);

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <wchar.h>

int main(void)
{
    setlocale(LC_ALL, "");

    char mbstr[] = "Hello, world!";
    wchar_t wc;
    int len = mbtowc(&wc, mbstr, sizeof(mbstr));
    if (len > 0) {
        wprintf(L"%lc\n", wc);
    } else if (len == 0) {
        wprintf(L"Empty string.\n");
    } else if (len == -1) {
        wprintf(L"Invalid multibyte character.\n");
    }

    return EXIT_SUCCESS;
}

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

int main(void)
{
    char src[] = "Hello, world!";
    char dst[20];
    memset(dst, 0, sizeof(dst));

    char *p = (char*) memccpy(dst, src, 'o', sizeof(src));
    if (p) {
        printf("'%c' found at index %ld\n", *(p - 1), p - dst - 1);
    } else {
        printf("'%c' not found\n", 'o');
    }

    printf("%s\n", dst);

    return 0;
}

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

int main(void)
{
    char str[] = "Hello, world!";
    char ch = 'w';
    char *p;

    // 在字符串中查找指定字符
    p = (char*) memchr(str, ch, strlen(str));
    if (p) {
        printf("'%c' found at index %ld\n", ch, p - str);
    } else {
        printf("'%c' not found\n", ch);
    }

    return EXIT_SUCCESS;
}

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

int main(void)
{
    char src[] = "Hello, world!";
    char dst[20];
    memset(dst, 0, sizeof(dst));

    // 将源字符串复制到目标字符串中
    memcpy(dst, src, strlen(src));

    printf("%s\n", dst);

    return 1;
}

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

int main(void)
{
    char str1[] = "Hello, world!";
    char str2[] = "Hello, everyone!";

    // 比较两个字符串
    int result = memcmp(str1, str2, strlen(str1));
    printf("result = %d\n", result);
    if (result == 0) {
        printf("Strings are equal\n");
    } else if (result < 0) {
        printf("String '%s' is smaller than string '%s'\n", str1, str2);
    } else {
        printf("String '%s' is larger than string '%s'\n", str1, str2);
    }

    return 1;
}

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

int main(void)
{
    char str[] = "Hello, world!";
    char tmp[20];
    memset(tmp, 0, sizeof(tmp));

    // 将源字符串复制到目标字符串中（处理重叠的情况）
    memmove(tmp, str + 6, strlen(str) - 6);

    printf("%s\n", tmp);

    return 0;
}

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

int main(void)
{
    char str[21] = {'\0'};
    memset(str, 'A', sizeof(str) - 1);
    printf("%s\n", str);
    return 0;
}