turbo c 2.0、borland c++库函数及用例.01

经典C教程,带所有ANSI C的库函数说明及例子

{   FILE *stream;
   char msg[] = "This is a test";   /* create a file */
   stream = fopen("DUMMY.FIL", "w");   /* write some data to the file */
   fwrite(msg, strlen(msg), 1, stream);   clrscr();
   printf("Press any key to flush\
	DUMMY.FIL:");
   getch();   /* flush the data to DUMMY.FIL without\
      closing it */
   flush(stream);   printf("\nFile was flushed, Press any key\
	to quit:");
   getch();
   return 0;
}void flush(FILE *stream)
{
     int duphandle;     /* flush the stream's internal buffer */
     fflush(stream);     /* make a duplicate file handle */
     duphandle = dup(fileno(stream));     /* close the duplicate handle to flush\
      the DOS buffer */
     close(duphandle);
}
函数名: fgetc
功  能: 从流中读取字符
用  法: int fgetc(FILE *stream);
程序例:#include <string.h>
#include <stdio.h>
#include <conio.h>int main(void)
{
   FILE *stream;
   char string[] = "This is a test";
   char ch;   /* open a file for update */
   stream = fopen("DUMMY.FIL", "w+");
   /* write a string into the file */
   fwrite(string, strlen(string), 1, stream);
   /* seek to the beginning of the file */
   fseek(stream, 0, SEEK_SET);
   do
   {
      /* read a char from the file */
      ch = fgetc(stream);      /* display the character */
      putch(ch);
   } while (ch != EOF);   fclose(stream);
   return 0;
}
函数名: fgetchar
功  能: 从流中读取字符
用  法: int fgetchar(void);
程序例:#include <stdio.h>int main(void)
{
   char ch;
   /* prompt the user for input */
   printf("Enter a character followed by \
	<Enter>: ");
   /* read the character from stdin */   ch = fgetchar();
   /* display what was read */
   printf("The character read is: '%c'\n",
	ch);
   return 0;
}
函数名: fgetpos
功  能: 取得当前文件的句柄
用  法: int fgetpos(FILE *stream);
程序例:#include <string.h>
#include <stdio.h>int main(void)
{
   FILE *stream;
   char string[] = "This is a test";
   fpos_t filepos;
   /* open a file for update */
   stream = fopen("DUMMY.FIL", "w+");   /* write a string into the file */
   fwrite(string, strlen(string), 1, stream);   /* report the file pointer position */
   fgetpos(stream, &filepos);
   printf("The file pointer is at byte\
	%ld\n", filepos);   fclose(stream);
   return 0;
}
函数名: fgets
功  能: 从流中读取一字符串
用  法: char *fgets(char *string, int n, FILE *stream);
程序例:#include <string.h>
#include <stdio.h>int main(void)
{
   FILE *stream;
   char string[] = "This is a test";
   char msg[20];
   /* open a file for update */   stream = fopen("DUMMY.FIL", "w+");
   /* write a string into the file */
   fwrite(string, strlen(string), 1, stream);
   /* seek to the start of the file */
   fseek(stream, 0, SEEK_SET);
   /* read a string from the file */
   fgets(msg, strlen(string)+1, stream);   /* display the string */
   printf("%s", msg);   fclose(stream);
   return 0;
}
函数名: filelength
功  能: 取文件长度字节数
用  法: long filelength(int handle);
程序例:#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>int main(void)
{
   int handle;
   char buf[11] = "0123456789";   /* create a file containing 10 bytes */
   handle = open("DUMMY.FIL", O_CREAT);
   write(handle, buf, strlen(buf));   /* display the size of the file */
   printf("file length in bytes: %ld\n",
	filelength(handle));   /* close the file */
   close(handle);
   return 0;
}
函数名: fillellipse
功  能: 画出并填充一椭圆
用  法: void far fillellipse( int x, int y, int xradius,
			      int yradius );
程序例:#include <graphics.h>
#include <conio.h>int main(void)
{
   int gdriver = DETECT, gmode;
   int xcenter, ycenter, i;
   initgraph(&gdriver,&gmode,"");
   xcenter = getmaxx() / 2;
   ycenter = getmaxy() / 2;   for (i=0; i<13; i++)
   {
      setfillstyle(i,WHITE);
      fillellipse(xcenter,ycenter,100,50);
      getch();
   }
   closegraph();
   return 0;
}
函数名: fillpoly
功  能: 画并填充一个多边形
用  法: void far fillpoly( int numpoints,
			   int far *polypoints );
程序例:#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>int main(void)
{
   /* request auto detection */   int gdriver = DETECT, gmode, errorcode;
   int i, maxx, maxy;   /* our polygon array */
   int poly[8];   /* initialize graphics, 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 */
   }
   maxx = getmaxx();
   maxy = getmaxy();   poly[0] = 20;        /* 1st vertext */
   poly[1] = maxy / 2;
   poly[2] = maxx - 20; /* 2nd */
   poly[3] = 20;   poly[4] = maxx - 50; /* 3rd */
   poly[5] = maxy - 20;
   /*
      4th vertex. fillpoly automatically
      closes the polygon.
   */
   poly[6] = maxx / 2;
   poly[7] = maxy / 2;   /* loop through the fill patterns */
   for (i=EMPTY_FILL; i<USER_FILL; i++)
   {
      /* set fill pattern */
      setfillstyle(i, getmaxcolor());      /* draw a filled polygon */
      fillpoly(4, poly);
      getch();
   }   /* clean up */
   closegraph();
   return 0;
}
函数名: findfirst
功  能: 搜索磁盘目录; 取得下一个匹配的findfirst模式的文件
用  法: int findfirst( char *pathname, struct ffblk *ffblk,
		       int attrib);
程序例:/* findfirst example */
#include <stdio.h>
#include <dir.h>
int main(void)
{
   struct ffblk ffblk;   int done;
   printf("Directory listing of *.*\n");
   done = findfirst("*.*",&ffblk,0);
   while (!done)
   {
      printf("  %s\n", ffblk.ff_name);
      done = findnext(&ffblk);
   }
   return 0;
}
函数名: findnext
功  能: 搜索磁盘目录; 取得下一个匹配的findfirst模式的文件
用  法: int findnext(struct ffblk *ffblk);
程序例:
/* findnext example */#include <stdio.h>
#include <dir.h>int main(void)
{
   struct ffblk ffblk;
   int done;
   printf("Directory listing of *.*\n");   done = findfirst("*.*",&ffblk,0);
   while (!done)
   {
      printf("  %s\n", ffblk.ff_name);
      done = findnext(&ffblk);
   }
   return 0;
}
函数名: floodfill
功  能: 填充一个有界区域
用  法: void far floodfill(int x, int y, int border);
程序例:#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>int main(void)
{
   /* request auto detection */
   int gdriver = DETECT, gmode, errorcode;   int maxx, maxy;   /* initialize graphics, 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 */
   }
   maxx = getmaxx();
   maxy = getmaxy();   /* select drawing color */
   setcolor(getmaxcolor());   /* select fill color */
   setfillstyle(SOLID_FILL, getmaxcolor());   /* draw a border around the screen */
   rectangle(0, 0, maxx, maxy);   /* draw some circles */
   circle(maxx / 3, maxy /2, 50);
   circle(maxx / 2, 20, 100);
   circle(maxx-20, maxy-50, 75);
   circle(20, maxy-20, 25);   /* wait for a key */
   getch();   /* fill in bounded region */
   floodfill(2, 2, getmaxcolor());   /* clean up */
   getch();   closegraph();
   return 0;
}
函数名: floor
功  能: 向下舍入
用  法: double floor(double x);
程序例:#include <stdio.h>
#include <math.h>int main(void)
{
   double number = 123.54;
   double down, up;   down = floor(number);   up = ceil(number);   printf("original number     %10.2lf\n",
	number);
   printf("number rounded down %10.2lf\n",
	down);
   printf("number rounded up   %10.2lf\n",
	up);   return 0;
}
函数名: flushall
功  能: 清除所有缓冲区
用  法: int flushall(void);
程序例:#include <stdio.h>int main(void)
{
   FILE *stream;   /* create a file */
   stream = fopen("DUMMY.FIL", "w");
   /* flush all open streams */   printf("%d streams were flushed.\n",
	flushall());
   /* close the file */
   fclose(stream);
   return 0;
}
函数名: fmod
功  能: 计算x对y的模, 即x/y的余数
用  法: double fmod(double x, double y);
程序例:#include <stdio.h>
#include <math.h>int main(void)
{
   double x = 5.0, y = 2.0;
   double result;   result = fmod(x,y);   printf("The remainder of (%lf / %lf) is \
	%lf\n", x, y, result);
   return 0;
}
函数名: fnmerge
功  能: 建立新文件名
用  法: void fnerge(char *path, char *drive, char *dir);
程序例:#include <string.h>
#include <stdio.h>
#include <dir.h>int main(void)
{
    char s[MAXPATH];
    char drive[MAXDRIVE];
    char dir[MAXDIR];    char file[MAXFILE];
    char ext[MAXEXT];    getcwd(s,MAXPATH); /*get the current working directory*/
    strcat(s,"\\");    /*append on a trailing character*/
    fnsplit(s,drive,dir,file,ext);
		    /* split the string to separate elems */
    strcpy(file,"DATA");
    strcpy(ext,".TXT");
    fnmerge(s,drive,dir,file,ext);
	     /* merge everything into one string */
    puts(s); /* display resulting string */
    return 0;
}
函数名: fopen
功  能: 打开一个流
用  法: FILE *fopen(char *filename, char *type);
程序例:#include <stdlib.h>
#include <stdio.h>
#include <dir.h>int main(void)
{
    char *s;
    char drive[MAXDRIVE];
    char dir[MAXDIR];    char file[MAXFILE];
    char ext[MAXEXT];
    int flags;    s=getenv("COMSPEC");
		/* get the comspec environment parameter */
    flags=fnsplit(s,drive,dir,file,ext);    printf("Command processor info:\n");
    if(flags & DRIVE)
       printf("\tdrive: %s\n",drive);
    if(flags & DIRECTORY)
       printf("\tdirectory: %s\n",dir);    if(flags & FILENAME)
       printf("\tfile: %s\n",file);
    if(flags & EXTENSION)
       printf("\textension: %s\n",ext);    return 0;
}
函数名: fprintf
功  能: 传送格式化输出到一个流中
用  法: int fprintf( FILE *stream,
		     char *format[, argument,...] );
程序例:/* Program to create backup of the
   AUTOEXEC.BAT file */#include <stdio.h>int main(void)
{
   FILE *in, *out;   if ((in = fopen("\\AUTOEXEC.BAT", "rt"))
       == NULL)
   {
      fprintf(stderr, "Cannot open input \
	    file.\n");
      return 1;
   }
   if ((out = fopen("\\AUTOEXEC.BAK", "wt"))
       == NULL)
   {  fprintf(stderr, "Cannot open output \
	    file.\n");
      return 1;
   }   while (!feof(in))
      fputc(fgetc(in), out);
   fclose(in);
   fclose(out);
   return 0;
}
函数名: FP_OFF
功  能: 获取远地址偏移量
用  法: unsigned FP_OFF(void far *farptr);
程序例:/* FP_OFF */#include <dos.h>
#include <stdio.h>int main(void)
{
   char *str = "fpoff.c";
   printf("The offset of this file in memory\
	is: %Fp\n", FP_OFF(str));   return 0;
}
函数名: FP_SEG
功  能: 获取远地址段值
用  法: unsigned FP_SEG(void far *farptr);
程序例:/* FP_SEG */#include <dos.h>
#include <stdio.h>int main(void)
{
   char *filename = "fpseg.c";
   printf("The offset of this file in memory\
	is: %Fp\n", FP_SEG(filename));   return(0);
}
函数名: fputc
功  能: 送一个字符到一个流中
用  法: int fputc(int ch, FILE *stream);
程序例:
#include <stdio.h>int main(void)
{
   char msg[] = "Hello world";
   int i = 0;   while (msg[i])
   {
      fputc(msg[i], stdout);      i++;
   }
   return 0;
}
函数名: fputchar
功  能: 送一个字符到标准输出流(stdout)中
用  法: int fputchar(char ch);
程序例:#include <stdio.h>int main(void)
{
   char msg[] = "This is a test";
   int i = 0;
   while (msg[i])
   {
      fputchar(msg[i]);      i++;
   }
   return 0;
}
函数名: fputs
功  能: 送一个字符到一个流中
用  法: int fputs(char *string, FILE *stream);
程序例:#include <stdio.h>
int main(void)
{
   /* write a string to standard output */
   fputs("Hello world\n", stdout);
   return 0;
}
函数名: fread
功  能: 从一个流中读数据
用  法: int fread( void *ptr, int size, int nitems,
		   FILE *stream );
程序例:#include <string.h>
#include <stdio.h>int main(void)
{
   FILE *stream;
   char msg[] = "this is a test";
   char buf[20];   if ((stream = fopen("DUMMY.FIL", "w+"))
       == NULL)
   {
      fprintf(stderr,
	    "Cannot open output file.\n");
      return 1;
   }
   /* write some data to the file */
   f