C语言函数大全--n 开头的函数

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

int main(void)
{
    double x = 0.0 / 0.0;  // 使用除 0 运算符来生成 NaN 数字
    printf("x: %f\n", x);

    double y = nan(NULL);  // 使用 nan() 函数来生成 NaN 数字
    printf("y: %f\n", y);

    return 0;
}

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

int main(void)
{
    struct timespec req = { 0 };
    req.tv_sec = 2;         // 等待时间为 2 秒
    req.tv_nsec = 5000000;  // 加上 5 毫秒

    int ret = nanosleep(&req, NULL);
    if (ret == 0) {
        printf("nanosleep completed\n");
    } else {
        printf("nanosleep interrupted by signal\n");
    }

    return 0;
}

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

int main(void)
{
    double x = 2.3;
    double y = -1.8;

    double z = nearbyint(x);   // 将 2.3 四舍五入到 2
    double w = nearbyint(y);   // 将 -1.8 四舍五入到 -2

    printf("x: %lf, nearbyint(x): %lf\n", x, z);
    printf("y: %lf, nearbyint(y): %lf\n", y, w);

    float xf = 2.5;
    printf("xf: %f, nearbyintf(xf): %f\n", xf, nearbyintf(xf));

    long double xL = -1.3;
    printf("xL: %Lf, nearbyintl(xL): %Lf\n", xL, nearbyintl(xL));

    return 0;
}

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

int main(void)
{
    double x = 1.0;
    double y = 2.0;

    printf("nextafter(%lf, %lf): %.20lf\n", x, y, nextafter(x, y));      
    printf("nextafter(%lf, %lf): %.20lf\n", y, x, nextafter(y, x));

    float xf = 2.0;
    float yf = 1.0;
    printf("nextafterf(%f, %f): %.20f\n", xf, yf, nextafterf(xf, yf));   

    long double xL = -1.2;
    long double yL = - 1.5;   
    printf("nextafterl(%Lf, %Lf): %.20Lf\n", xL, yL, nextafterl(xL, yL));      

    return 0;
}

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

int main(void)
{
    double x = 1.0;
    long double y = 2.0;

    printf("nexttoward(%lf, %Lf): %.20lf\n", x, y, nexttoward(x, y)); 

    float xf = 3.2;
    printf("nexttowardf(%f, %Lf): %.20f\n", xf, y, nexttowardf(xf, y)); 

    long double xL = 1.9;
    printf("nexttowardl(%Lf, %Lf): %.20Lf\n", xL, y, nexttowardl(xL, y)); 

    return 0;
}

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

int main()
{
    // 创建一个新的本地化环境变量，用于解析德语字符串比较和排序规则。
    locale_t loc = newlocale(LC_COLLATE_MASK, "de_DE.UTF-8", LC_GLOBAL_LOCALE);

    // 在新的本地化环境变量下比较两个字符串，并输出比较结果。
    const char *str1 = "äbc";
    const char *str2 = "abc";
    int result = strcoll_l(str1, str2, loc);
    printf("%s %s %s\n", str1, (result < 0 ? "<" : (result > 0 ? ">" : "==")), str2);

    // 释放本地化环境变量
    freelocale(loc);

    return 0;
}

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

static int count = 0;

int print_file_info(const char *fpath, const struct stat *sb, int typeflag, struct FTW *ftwbuf)
{
    // 打印文件路径和类型
    printf("%s ", fpath);
    if (typeflag == FTW_F) {
        printf("(file)\n");
    } else if (typeflag == FTW_D) {
        printf("(dir)\n");
    } else {
        printf("(other)\n");
    }

    // 计数器加一
    count++;

    return 0;
}

int main(void)
{
    int result = nftw(".", print_file_info, 10, FTW_PHYS);

    if (result == -1) {
        perror("nftw");
        exit(EXIT_FAILURE);
    }

    printf("Total files and directories: %d\n", count);

    return 0;
}

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

int main(void)
{
    // 输出当前进程的初始优先级
    printf("Initial nice value: %d\n", nice(0));

    // 将进程的优先级减少 10
    int result = nice(10);
    if (result == -1) {
        perror("nice");
    } else {
        printf("New nice value: %d\n", result);
    }

    return 0;
}

#include <stdio.h>
#include <langinfo.h>

int main(void)
{
    char *time_fmt = nl_langinfo(T_FMT);
    char *date_fmt = nl_langinfo(D_FMT);

    printf("Time format: %s\n", time_fmt);
    printf("Date format: %s\n", date_fmt);

    return 0;
}

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

int main(void)
{
    unsigned short seed[3];
    seed[0] = (unsigned short) time(NULL);
    seed[1] = (unsigned short) getpid();
    seed[2] = 12345;

    srand48(seed);

    printf("Random number: %ld\n", nrand48(seed));

    return 0;
}

#include <stdio.h>
#include <stdint.h>
#include <netinet/in.h>

int main(void)
{
    uint32_t num1 = 0x12345678;
    uint16_t num2 = 0x5678;

    printf("Original value (hex):\n");
    printf("num1: %08X\n", num1);
    printf("num2: %04X\n", num2);

    num1 = ntohl(num1);
    num2 = ntohs(num2);

    printf("Converted value (hex):\n");
    printf("num1: %08X\n", num1);
    printf("num2: %04X\n", num2);

    return 0;
}