C语言函数大全--r 开头的函数

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

void sigint_handler(int sig) {
    printf("Caught signal %d\n", sig);
    exit(0);
}

int main() {
    signal(SIGINT, sigint_handler);

    while (1) {
        printf("Doing something...\n");
        getchar();
        // check for interrupt signal
        raise(SIGINT);
    }

    return 0;
}

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

int main() {
    // 使用系统时间作为随机数种子初始化
    srand(time(NULL));

    // 生成并输出 10 个随机数
    for (int i = 0; i < 10; i++) {
        printf("%d\n", rand());
    }

    return 0;
}

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

#define BUFFER_SIZE 1024

int main() {
    char buffer[BUFFER_SIZE];
    ssize_t num_read;

    num_read = read(STDIN_FILENO, buffer, BUFFER_SIZE);
    if (num_read == -1) {
        perror("read");
        return 1;
    }

    printf("Read %ld bytes from standard input: %.*s", num_read, (int)num_read, buffer);

    return 0;
}

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

int main() {
    // 分配 10 个整型变量的内存空间
    int *p = (int*) malloc(10 * sizeof(int));
    if (p == NULL) {
        printf("内存分配失败\n");
        exit(1);
    }

    // 更改为 20 个整型变量的内存空间
    int *q = (int*) realloc(p, 20 * sizeof(int));
    if (q == NULL) {
        printf("内存分配失败\n");
        exit(1);
    }

    // 输出新的内存地址
    printf("原内存地址：%p，新内存地址：%p\n", p, q);

    // 释放新分配的内存空间
    free(q);

    return 0;
}

#include <graphics.h>

int main(void)
{
    int gdriver = DETECT, gmode;
    int left, top, right, bottom;

    initgraph(&gdriver, &gmode, "");

    left = getmaxx() / 2 - 50;
    top = getmaxy() / 2 - 50;
    right = getmaxx() / 2 + 50;
    bottom = getmaxy() / 2 + 50;

    rectangle(left,top,right,bottom);

    getch();
    closegraph();
    return 0;
}

#include <graphics.h>

int main()
{
    int gd = DETECT, gm;
    initgraph(&gd, &gm, "");
    registerbgidriver(EGAVGA_driver); // 注册EGAVGA驱动程序
    circle(100, 100, 50); // 绘制圆形
    getch(); // 等待用户输入
    closegraph(); // 关闭图形界面
    return 0;
}

#include <stdio.h>

int main()
{
    int result;
    char filename[] = "example.txt";
    result = remove(filename);
    if (result == 0)
    {
        printf("The file %s has been removed.\n", filename);
    }
    else
    {
        printf("Error deleting the file %s.\n", filename);
    }
    return 0;
}

#include <stdio.h>

int main()
{
    char oldname[] = "temp.txt";
    char newname[] = "tempnew.txt";
    int result;
    
    result = rename(oldname, newname);
    
    if (result == 0)
    {
        printf("The file has been renamed.\n");
    }
    else
    {
        printf("Error renaming the file.\n");
    }
    
    return 0;
}

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

int main(void)
{
    int gdriver = DETECT, gmode;
    int x, y;

    initgraph(&gdriver, &gmode, "");

    x = getmaxx() / 2;
    y = getmaxy() / 2;

    settextjustify(CENTER_TEXT, CENTER_TEXT);
    outtextxy(x, y, "Press any key to exit graphics:");
    getch();

    // 将图形模式恢复到文本模式
    restorecrtmode();
    printf("We're now in text mode.\n");
    printf("Press any key to return to graphics mode:");
    getch();

    // 返回图形模式
    setgraphmode(getgraphmode());

    settextjustify(CENTER_TEXT, CENTER_TEXT);
    outtextxy(x, y, "We're back in graphics mode.");
    outtextxy(x, y+textheight("W"), "Press any key to halt:");

    getch();
    closegraph();
    return 0;
}

#include <stdio.h>

int main() {
    FILE *fp = fopen("tempnew.txt", "r");
    if (fp == NULL) {
        perror("Failed to open file");
        return 1;
    }
    
    // 读取文件内容
    char buffer[1024];
    while (fgets(buffer, sizeof(buffer), fp)) {
        printf("%s", buffer);
    }

    printf("\n");
    
    // 将文件指针重置到开头
    rewind(fp);
    
    // 再次读取文件内容
    while (fgets(buffer, sizeof(buffer), fp)) {
        printf("%s", buffer);
    }
    
    fclose(fp);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
int main() {
    const char *dir_name = "test";
    if (mkdir(dir_name) I= 0) {
        perror("Failed to create directory");
        return 1;
    }

    //在目录中创建一些文件
    FILE *fp1 = fopen("test/file1.txt","w");
    FILE *fp2 = fopen("test/file2.txt","w");
    fclose(fp1);
    fclose(fp2);
    
    /／尝试刪除非空目录
    if (rmdir(dir name) |= 0) {
        perror("Failed to remove directory");
        return 1;
    }
    printf("Directory removed successfullyIn");
    return 0;
}

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

int main() {
    double x = 3.14159265;
    
    double rounded1 = round(x);     // 将 x 四舍五入为整数，结果为 3
    double rounded2 = round(x * 100) / 100;  // 将 x 精确到小数点后两位，结果为 3.14
    
    printf("rounded1: %lf\n", rounded1);
    printf("rounded2: %lf\n", rounded2);

    float xf = 2.5;
    printf("rountf(%f) = %f\n", xf, roundf(xf)); // 将 xf 四舍五入为整数，结果为 3
    
    long double xL = 2.4;
    printf("rountl(%Lf) = %Lf", xL, roundl(xL)); // 将 xL 四舍五入为整数，结果为 2
    return 0;
}

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

int main() {
    double x = 10.5, y = 3.2;
    printf("remainder(%lf, %lf) = %.20lf\n", x, y, remainder(x, y));


    float xf = 10.5f, yf = 3.2f;
    printf("remainder(%f, %f) = %.20f\n", xf, yf, remainderf(xf, yf));


    long double xL = 10.5L, yL = 3.2L;
    printf("remainder(%Lf, %Lf) = %.20Lf\n", xL, yL, remainderl(xL, yL));
    return 0;
}

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

int main() {
    int quo;
    double x = 10.5, y = 3.2;
    double rem = remquo(x, y, &quo);
    printf("remquo(%lf, %lf, quo) = %.20lf, quo = %d\n", x, y, rem, quo);

    float xf = 10.5f, yf = 3.2f;
    float remf = remquof(xf, yf, &quo);
    printf("remquof(%f, %f, quo) = %.20f, quo = %d\n", xf, yf, remf, quo);

    long double xL = 10.5L, yL = 3.2L;
    long double remL = remquol(xL, yL, &quo);
    printf("remquol(%Lf, %Lf, quo) = %.20Lf, quo = %d\n", xL, yL, remL, quo);

    return 0;
}

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

int main() {
    double d = 3.7;
    float f = 2.4f;
    long double ld = 5.9L;

    printf("rint(%f) = %.1f\n", d, rint(d));   // Output: rint(3.700000) = 4.0
    printf("rintf(%f) = %.1f\n", f, rintf(f)); // Output: rintf(2.400000) = 2.0
    printf("rintl(%Lf) = %.1Lf\n", ld, rintl(ld)); // Output: rintl(5.900000) = 6.0

    return 0;
}