在C语言中，有哪些以'd'开头的函数可以实现什么功能？

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C语言函数大全——d开头函数

1.detectgraph

1.1 函数说明

函数声明：void detectgraph(int *graphdriver, int *graphmode);功能：通过检测硬件确定图形驱动程序和模式

1.2 示例cvoid detectgraph(int *graphdriver, int *graphmode) { // 检测硬件并设置graphdriver和graphmode的值}

C语言函数大全

本篇介绍C语言函数大全--d开头的函数

1. detectgraph

1.1 函数说明

函数声明 函数功能 void detectgraph(int *graphdriver, int *graphmode); 通过检测硬件确定图形驱动程序和模式

1.2 演示示例

#include <graphics.h> #include <stdlib.h> #include <stdio.h> #include <conio.h> /* names of the various cards supported */ char *dname[] = { "requests detection", "a CGA", "an MCGA", "an EGA", "a 64K EGA", "a monochrome EGA", "an IBM 8514", "a Hercules monochrome", "an AT&T 6300 PC", "a VGA", "an IBM 3270 PC" }; int main(void) { /* returns detected hardware info. */ int gdriver, gmode, errorcode; /* detect graphics hardware available */ detectgraph(&gdriver, &gmode); /* initialize graphics and local variables */ initgraph(&gdriver, &gmode, ""); /* read result of detectgraph call */ 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 */ } /* display the information detected */ printf("You have [%s] video display card.\n", dname[gdriver]); printf("Press any key to halt:"); getch(); return 0; }

1.3 运行结果

2. difftime

2.1 函数说明

函数声明 函数功能 double difftime(time_t time2, time_t time1); 计算两个时刻之间的时间差

2.2 演示示例

#include <stdio.h> #include <time.h> int main(void) { time_t first, second; // time_t 相当于 long first = time(NULL); // Gets system time getchar(); second = time(NULL); // Gets system time again printf("The difference is: %lf seconds\n", difftime(second, first)); return 0; }

2.3 运行结果

3. div

3.1 函数说明

函数声明 函数功能 div_t (int number, int denom); 将两个整数相除, 返回商和余数

3.2 演示示例

#include <stdio.h> #include <math.h> int main(void) { div_t x = div(10,3); // 商 和 余数 printf("10 div 3 = %d remainder %d\n", x.quot, x.rem); return 0; }

3.3 运行结果

4. drawpoly

4.1 函数说明

函数声明 函数功能 void drawpoly(int numpoints, int *polypoints); 画多边形

4.2 演示示例

#include <graphics.h> #include <stdio.h> int main(void) { // request auto detection int gdriver = DETECT, gmode, errorcode; int maxx, maxy; // our polygon array int poly[10]; // 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(); // terminate with an error code exit(1); } maxx = getmaxx(); maxy = getmaxy(); poly[0] = 20; poly[1] = maxy / 2; poly[2] = maxx - 20; poly[3] = 20; poly[4] = maxx - 50; poly[5] = maxy - 20; poly[6] = maxx / 2; poly[7] = maxy / 2; // drawpoly doesn't automatically close the polygon, so we close it. poly[8] = poly[0]; poly[9] = poly[1]; // draw the polygon drawpoly(5, poly); // clean up getch(); closegraph(); return 0; }

4.3 运行结果

5. dup

5.1 函数说明

函数声明 函数功能 int dup(int handle); 复制文件描述符；若成功为新的文件描述，若出错为-1

dup 返回的新文件描述符一定是当前可用文件描述中的最小数值。

5.2 演示示例

#include <sys/types.h> #include <sys/stat.h> #include <string.h> #include <stdio.h> #include <conio.h> #include <fcntl.h> #include <io.h> void flush(FILE *stream); int main(void) { FILE *fp; char msg[] = "This is a test"; /* create a file */ fp = fopen("STU.FIL", "w"); /* write some data to the file */ fwrite(msg, strlen(msg), 1, fp); int handle; handle = open("temp.txt", _O_RDWR | _O_CREAT, _S_IREAD | _S_IWRITE); printf("file hanlde : %d\n", handle); printf("Press any key to flush STU.FIL:"); getchar(); /* flush the data to STU.FIL without closing it */ flush(fp); printf("\nFile was flushed, Press any key to quit:"); getchar(); return 0; } void flush(FILE *stream) { int duphandle; /* flush TC's internal buffer */ fflush(stream); /* make a duplicate file handle */ duphandle = dup(fileno(stream)); printf("duplicate file hanlde : %d", duphandle); /* close the duplicate handle to flush the DOS buffer */ close(duphandle); }

5.3 运行结果

6. dup2

6.1 函数说明

函数声明 函数功能 int dup2(int oldhandle, int newhandle); 复制文件描述符；若成功为新的文件描述，若出错为-1。

dup2 可以用 newhandle 参数指定新的描述符数值。如果 newhandle 已经打开，则先关闭。若 oldhandle = newhandle，则 dup2 返回 newhandle，而不关闭它。

6.2 演示示例

#include <sys\stat.h> #include <stdio.h> #include <string.h> #include <fcntl.h> #include <io.h> int main(void) { #define STDOUT 1 int handle, oldstdout; char msg[] = "This is a test1"; /* create a file */ handle = open("STU.FIL", O_CREAT | O_RDWR, S_IREAD | S_IWRITE); printf("open file handle : %d\n", handle); /* create a duplicate handle for standard output */ oldstdout = dup(STDOUT); printf("dup file handle : %d", oldstdout); /* redirect standard output to STU.FIL by duplicating the file handle onto the file handle for standard output. */ dup2(handle, STDOUT); /* close the handle for STU.FIL */ close(handle); /* will be redirected into STU.FIL */ write(STDOUT, msg, strlen(msg)); /* restore original standard output handle */ dup2(oldstdout, STDOUT); /* close duplicate handle for STDOUT */ close(oldstdout); return 0; }

6.3 运行结果

参考

1. [API Reference Document]