总览

1. cbrt，cbrtf，cbrtl

1.1 函数说明

1.2 演示示例

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

int main(void)
{
   
   
    double x = 8.0;
    float xf = 27.0;
    long double xL = 64.0;

    // 立方根
    printf("The cube root of the double value %.4lf is %.4lf\n", x, cbrt(x));
    printf("The cube root of the float value %.4f is %.4f\n", xf, cbrtf(xf));
    printf("The cube root of the long double value %.4Lf is %.4Lf", xL, cbrtl(xL));    

    return 0;
}

1.3 运行结果

2. ceil，ceilf，ceill

2.1 函数说明

2.2 演示示例

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

int main(void)
{
   
   
    double x = 2.3;
    float xf = 2.5;
    long double xL = 2.8;

    // 计算大于或等于x的最小整数
    printf("The minimum integer greater than or equal to the [x = %.4lf] is %.4lf\n", x, ceil(x));
    printf("The minimum integer greater than or equal to the [x = %.4f]  is %.4f\n", xf, ceilf(xf));
    printf("The minimum integer greater than or equal to the [x = %.4Lf] is %.4Lf", xL, ceill(xL));    
    return 0;
}

2.3 运行结果

3. copysign，copysignf，copysignl

3.1 函数说明

copysign 是一个数学函数，用于返回一个具有特定绝对值和符号的浮点数。它接受两个参数：第一个参数x是数值，第二个参数y是符号。该函数返回一个新的数，其值大小与x相同，但符号与y相同。这意味着如果y是正数，则结果与x相同；如果y是负数，则结果为x的相反数。

copysign 函数在数值分析和信号处理等领域非常有用，因为它允许程序员根据需要修改数据的符号而不改变其绝对大小。

3.2 演示示例

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

int main(void)
{
   
   
    double x = 2.0, y = -1.0;
    float xf = 2.0, yf = -1.0;
    long double xL = 2.0, yL = -1.0;

    // 通过组合x的大小和y的符号生成一个值
    printf("The double value by combining the magnitude of [x = %.4lf] and the sign of [y = %.4lf] is %.4lf\n", x, y, copysign(x, y));
    printf("The float value by combining the magnitude of [x = %.4f] and the sign of [y = %.4f] is %.4f\n", xf, yf, copysignf(xf, yf));
    printf("The long double value by combining the magnitude of [x = %.4Lf] and the sign of [y = %.4Lf] is %.4Lf", xL, yL, copysignl(xL, yL));    
    return 0;
}

3.3 运行结果

4. chdir

4.1 函数说明

4.2 演示示例

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

#define MAXDIR 1000
char old_dir[MAXDIR];
char new_dir[MAXDIR];

int main()
{
   
   
    if (!getcwd(old_dir, MAXDIR)) // 获取当前的目录
    {
   
   
        perror("getcwd()");
        exit(1);
    }
    printf("Current directory is: %s\n", old_dir); 

    if (chdir("D:\\")) // 切换目录，成功返回0，失败返回-1
    {
   
   
        perror("chdir()");
        exit(1);
    }

    if (!getcwd(new_dir, MAXDIR))
    {
   
   
        perror("getcwd()");
        exit(1);
    }
    printf("Current directory is now: %s\n", new_dir);

    printf("\nChanging back to orignal directory: %s\n", old_dir);

    if (chdir(old_dir))
    {
   
   
        perror("chdir()");
        exit(1);
    }

    return 0;
}

4.3 运行结果

5. chmod

5.1 函数说明

5.2 演示示例

#include <sys\stat.h>
#include <stdio.h>
#include <io.h>

void make_read_only(char *filename);

int main(void)
{
   
   
    make_read_only("NOTEXIST.FIL");
    make_read_only("students.txt");
    return 0;
}

void make_read_only(char *filename)
{
   
   
    int stat;

    stat = chmod(filename, S_IREAD);
    if (stat)
        printf("Couldn't make %s read-only\n", filename);
    else
        printf("Made %s read-only\n", filename);
}

5.3 运行结果

6. chsize

6.1 函数说明

6.2 演示示例

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main()
{
   
   
   int fh, result;
   unsigned int nbytes = 2048;
   // 打开文件
   if((fh=open("temp.txt", _O_RDWR | _O_CREAT, _S_IREAD | _S_IWRITE))  != -1)
   {
   
   
      printf("File length before: %ld\n", filelength(fh)); // 获取文件大小
      if((result=chsize(fh, nbytes))== 0)
         printf("Size successfully changed\n");
      else
         printf("Problem in changing the size\n");
      printf("File length after:  %ld\n", filelength(fh));
      close(fh);
   }
   return 0;
}

6.3 运行结果

7. circle

7.1 函数说明

7.2 演示示例

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

int main(void)
{
   
   
    /* request auto detection */
    int gdriver = DETECT, gmode, errorcode;
    int midx, midy;
    int radius = 100;

    /* initialize graphics and local variables */
    initgraph(&gdriver, &gmode, "");

    /* read result of initialization */
    errorcode = graphresult();
    if (errorcode != grOk)  /* an error occurred */
    {
   
   
      printf("Graphics error: %s\n", grapherrormsg(errorcode));
      printf("Press any key to halt:");
      getch();
      exit(1); /* terminate with an error code */
    }

    midx = getmaxx() / 2;
    midy = getmaxy() / 2;
    setcolor(getmaxcolor());

    /* draw the circle */
    circle(midx, midy, radius);

    /* clean up */
    getch();
    closegraph();
    return 0;
}

7.3 运行结果

8. cleardevice

8.1 函数说明

8.2 演示示例

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

int main(void)
{
   
   
    /* request auto detection */
    int gdriver = DETECT, gmode, errorcode;
    int midx, midy;

    /* initialize graphics and local variables */
    initgraph(&gdriver, &gmode, "");

    /* read result of initialization */
    errorcode = graphresult();
    if (errorcode != grOk)  /* an error occurred */
    {
   
   
        printf("Graphics error: %s\n", grapherrormsg(errorcode));
        printf("Press any key to halt:");
        getch();
        exit(1); /* terminate with an error code */
    }

    midx = getmaxx() / 2;
    midy = getmaxy() / 2;
    setcolor(getmaxcolor());

    /* for centering screen messages */
    settextjustify(CENTER_TEXT, CENTER_TEXT);

    /* output a message to the screen */
    outtextxy(midx, midy, "press any key to clear the screen:");

    /* wait for a key */
    getch();

    /* clear the screen */
    cleardevice();

    /* output another message */
    outtextxy(midx, midy, "press any key to quit:");

    /* clean up */
    getch();
    closegraph();
    return 0;
}

8.3 运行结果

9. clearerr

9.1 函数说明

9.2 演示示例

#include <stdio.h>

int main(void)
{
   
   
    FILE *fp;
    char ch;

    /* open a file for writing */
    fp = fopen("temp.txt", "w");

    /* force an error condition by attempting to read */
    ch = fgetc(fp);
    printf("%c\n",ch);

    int errorFlag = ferror(fp);
    printf("Error Flag : %d\n", errorFlag);
    if (errorFlag)
    {
   
   
        /* display an error message */
        printf("Error reading from temp.txt\n");

        /* reset the error and EOF indicators */
        clearerr(fp);
    }

    printf("Error Flag : %d", ferror(fp));

    fclose(fp);
    return 0;
}

9.3 运行结果

10. clearviewport

10.1 函数说明

10.2 演示示例

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

#define CLIP_ON 1   /* activates clipping in viewport */

int main(void)
{
   
   
    /* request auto detection */
    int gdriver = DETECT, gmode, errorcode;
    int ht;

    /* initialize graphics and local variables */
    initgraph(&gdriver, &gmode, "");

    /* read result of initialization */
    errorcode = graphresult();
    if (errorcode != grOk)  /* an error occurred */
    {
   
   
        printf("Graphics error: %s\n", grapherrormsg(errorcode));
        printf("Press any key to halt:");
        getch();
        exit(1); /* terminate with an error code */
    }

    setcolor(getmaxcolor());
    ht = textheight("W");

    /* message in default full-screen viewport */
    outtextxy(0, 0, "* <-- (0, 0) in default viewport");

    /* create a smaller viewport */
    setviewport(50, 50, getmaxx()-50, getmaxy()-50, CLIP_ON);

    /* display some messages */
    outtextxy(0, 0, "* <-- (0, 0) in smaller viewport");
    outtextxy(0, 2*ht, "Press any key to clear viewport:");

    /* wait for a key */
    getch();

    /* clear the viewport */
    clearviewport();

    /* output another message */
    outtextxy(0, 0, "Press any key to quit:");

    /* clean up */
    getch();
    closegraph();
    return 0;
}

10.3 运行结果

11. close

11.1 函数说明

11.2 演示示例

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>

int main()
{
   
   
    int handle;
    char buf[11] = "0123456789";

    /* create a file containing 10 bytes */
    handle = open("temp.txt", _O_RDWR | _O_CREAT, _S_IREAD | _S_IWRITE);
    if (handle > -1)
    {
   
   
        write(handle, buf, strlen(buf));
        printf("Write successfully\n");
        /* close the file */
        close(handle);
        printf("Close File successfully");
    }
    else
    {
   
   
        printf("Error opening file\n");
    }
    return 0;
}

11.3 运行结果

12. clock

12.1 函数说明

12.2 演示示例

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

int main(void)
{
   
   
    clock_t start, end;
    start = clock();
    printf("start = %ld\n", start);
    getchar();

    end = clock();
    printf("end = %ld\n", end);
    printf("The time was: %.3lfs\n", (double) (end - start) / CLK_TCK);

    return 0;
}

12.3 运行结果

13. closegraph

13.1 函数说明

13.2 演示示例

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

int main(void)
{
   
   
    /* request auto detection */
    int gdriver = DETECT, gmode, errorcode;
    int x, y;

    /* initialize graphics mode */
    initgraph(&gdriver, &gmode, "");

    /* read result of initialization */
    errorcode = graphresult();

    if (errorcode != grOk)  /* an error occurred */
    {
   
   
        printf("Graphics error: %s\n", grapherrormsg(errorcode));
        printf("Press any key to halt:");
        getch();
        exit(1); /* terminate with an error code */
    }

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

    /* output a message */
    settextjustify(CENTER_TEXT, CENTER_TEXT);
    outtextxy(x, y, "Press a key to close the graphics system:");

    /* wait for a key */
    getch();

    /* closes down the graphics system */
    closegraph();

    printf("We're now back in text mode.\n");
    printf("Press any key to halt:");
    getchar();
    return 0;
}

13.3 运行结果

14. cos，cosf，cosl

14.1 函数说明

14.2 演示示例

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

int main(void)
{
   
   
    double x = 1.0;
    double result = cos(x); // 余弦

    float xf = 1.0f;
    float resultf = cosf(xf);

    long double xL = 1.0;
    long double resultL = cosl(xL);

    printf("The cosine of %lf is %.16lf\n", x, result);
    printf("The cosine of %f is %.16f\n", xf, resultf);
    printf("The cosine of %Lf is %.16Lf\n", xL, resultL);

    return 0;
}

14.3 运行结果

15. cosh，coshf，coshl

15.1 函数说明

15.2 演示示例

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

int main(void)
{
   
   
    double x = 1.0;
    double result = cosh(x); // 双曲余弦

    float xf = 1.0f;
    float resultf = coshf(xf);

    long double xL = 1.0;
    long double resultL = coshl(xL);

    printf("The hyperbolic coshine of %lf is %.16lf\n", x, result);
    printf("The hyperbolic coshine of %f is %.16f\n", xf, resultf);
    printf("The hyperbolic coshine of %Lf is %.16Lf\n", xL, resultL);

    return 0;
}

15.3 运行结果

16. creat

16.1 函数说明

16.2 演示示例

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

int main(void)
{
   
   
   int handle;
   char buf[11] = "0123456789";

   handle = creat("temp1.txt", S_IREAD | S_IWRITE);

   printf("Create file successfully");

   /* write 10 bytes to the file */
   write(handle, buf, strlen(buf));

   /* close the file */
   close(handle);
   return 0;
}

16.3 运行结果

17. ctime

17.1 函数说明

17.2 演示示例

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

int main(void)
{
   
   
    time_t t;
    time(&t);
    printf("Today's date and time: %s\n", ctime(&t));
    return 0;
}

17.3 运行结果

参考

1. [API Reference Document]