C语言函数大全--m 开头的函数（下）

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>

int main() 
{
    int dirfd;
    if ((dirfd = open("/tmp", O_RDONLY)) == -1) 
    {
        printf("Error opening directory.\n");
        return 1;
    }

    if (mkdirat(dirfd, "testdir", S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH) == -1) 
    {
        printf("Error creating directory.\n");
        return 1;
    }

    close(dirfd);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>

int main() 
{
    // 如果函数调用成功，则在 /tmp 目录下创建一个名为 myfifo 的命名管道
    if (mkfifo("/tmp/myfifo", S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP) == -1) 
    {
        printf("Error creating named pipe.\n");
        return 1;
    }

    return 0;
}

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

int main() 
{
    char temp_file_template[] = "tmp/tempfile-XXXXXX";
    int fd;

    if ((fd = mkstemp(temp_file_template)) == -1) 
    {
        printf("Error creating temporary file.\n");
        return 1;
    }

    printf("Temporary file created: %s\n", temp_file_template);

    // 读写临时文件

    // 关闭临时文件
    close(fd);
    return 0;
}

#include <stdio.h>
#include <stdlib.h> 
#include <sys/stat.h>

int main() 
{
    if (mkdir("tmp/newdir") == -1) 
    {
        printf("Error creating new directory.\n");
        return 1;
    }

    return 0;
}

#include <stdio.h>
#include <stdlib.h> 
#include <sys/stat.h>
#include <sys/types.h>

int main() 
{
    if (mkdir("/tmp/newdir", S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH) == -1) 
    {
        printf("Error creating new directory.\n");
        return 1;
    }

    return 0;
}

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

int main() 
{
    struct tm my_time = {0};  // 初始化为 0，避免随机值影响结果
    my_time.tm_year = 2023 - 1900;  // 年份应该减去 1900
    my_time.tm_mon = 4 - 1;  // 月份从 0 开始计数，应该减去 1
    my_time.tm_mday = 15;
    my_time.tm_hour = 10;
    my_time.tm_min = 30;
    my_time.tm_sec = 0;

    time_t timestamp = mktime(&my_time);
    if (timestamp == -1) 
    {
        printf("Error converting time to timestamp.\n");
        return 1;
    }

    printf("Unix timestamp: %lld\n", timestamp);

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>   // memset 函数所需头文件
#include <sys/mman.h> // mlock 函数所需头文件

#define PAGE_SIZE 4096  // 页大小

int main() 
{
    char *buf;
    size_t size = PAGE_SIZE;

    // 分配一段内存并清零
    buf = (char *)malloc(size);
    memset(buf, 0, size);

    // 锁定分配的内存区域
    if (mlock(buf, size) == -1) 
    {
        printf("Error locking memory.\n");
        return 1;
    }

    // 使用分配的内存...
    strncpy(buf, "Hello world!", size);
    printf("%s\n", buf);

    // 解锁内存区域
    if (munlock(buf, size) == -1) 
    {
        printf("Error unlocking memory.\n");
        return 1;
    }

    free(buf);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>

int main() 
{
    int fd;
    char *ptr;

    // 打开文件
    if ((fd = open("example.txt", O_RDWR)) == -1) 
    {
        printf("Error opening file.\n");
        return 1;
    }

    // 将文件映射到内存中
    ptr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (ptr == MAP_FAILED) 
    {
        printf("Error mapping file.\n");
        return 1;
    }

    // 使用映射区域进行读写操作
    strncpy(ptr, "Hello world!", 13);
    printf("%s\n", ptr);

    // 取消映射并关闭文件
    if (munmap(ptr, 4096) == -1) 
    {
        printf("Error unmapping file.\n");
        return 1;
    }
    close(fd);

    return 0;
}

#include <stdio.h>
#include <math.h>

int main() 
{
    double x = 3.141592653589793;
    double ipart;

    double fpart = modf(x, &ipart);

    printf("x = %f\n", x);
    printf("整数部分 = %.0f\n", ipart);
    printf("小数部分 = %f\n", fpart);

    float y = 2.718281828459045;
    float ipart_f;

    float fpart_f = modff(y, &ipart_f);

    printf("y = %f\n", y);
    printf("整数部分 = %.0f\n", ipart_f);
    printf("小数部分 = %f\n", fpart_f);

    long double z = 1.414213562373095;
    long double ipart_l;

    long double fpart_l = modfl(z, &ipart_l);

    printf("z = %Lf\n", z);
    printf("整数部分 = %.0Lf\n", ipart_l);
    printf("小数部分 = %Lf\n", fpart_l);

    return 0;
}

#include <stdio.h>
#include <sys/mount.h>

int main() 
{
    int ret;
    const char* source = "/dev/sda1";
    const char* target = "/mnt/usbdrive";
    const char* type = "ext4";

    ret = mount(source, target, type, 0, NULL);
    if (ret == -1) 
    {
        perror("mount");
        return 1;
    }

    printf("File system mounted successfully!\n");

    return 0;
}

#include <stdio.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

int main() 
{
    int fd = open("example.txt", O_RDWR);
    if (fd == -1) 
    {
        perror("open");
        return 1;
    }

    // 将文件映射到内存中
    char* ptr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (ptr == MAP_FAILED) 
    {
        perror("mmap");
        close(fd);
        return 1;
    }

    // 写入新的数据
    strncpy(ptr, "Hello world!", 13);

    // 同步数据到文件中
    int ret = msync(ptr, 4096, MS_SYNC);
    if (ret == -1) 
    {
        perror("msync");
        munmap(ptr, 4096);
        close(fd);
        return 1;
    }

    // 解除映射并关闭文件
    ret = munmap(ptr, 4096);
    if (ret == -1) 
    {
        perror("munmap");
        close(fd);
        return 1;
    }
    close(fd);

    return 0;
}