c语言函数--F

函数名: fabs

功 能: 返回浮点数的绝对值

用 法: double fabs(double x);

程序例:

#include <stdio.h>
#include <math.h>
int main(void)
{
   float  number = -1234.0;
   printf("number: %f  absolute value: %f\n",
   number, fabs(number));
   return 0;
}

函数名: farcalloc

功 能: 从远堆栈中申请空间

用 法: void far *farcalloc(unsigned long units, unsigned ling unitsz);

程序例:

#include <stdio.h>
#include <alloc.h>
#include <string.h>
#include <dos.h>
int main(void)
{
   char far *fptr;
   char *str = "Hello";
   /* allocate memory for the far pointer */
   fptr = farcalloc(10, sizeof(char));
   /* copy "Hello" into allocated memory */
   /*
      Note: movedata is used because you
      might be in a small data model, in
      which case a normal string copy routine
      can not be used since it assumes the
      pointer size is near.
   */
   movedata(FP_SEG(str), FP_OFF(str),
     FP_SEG(fptr), FP_OFF(fptr),
            strlen(str));
   /* display string (note the F modifier) */
   printf("Far string is: %Fs\n", fptr);
   /* free the memory */
   farfree(fptr);
   return 0;
}

函数名: farcoreleft

功 能: 返回远堆中未作用存储区大小

用 法: long farcoreleft(void);

程序例:

#include <stdio.h>
#include <alloc.h>
int main(void)
{
   printf("The difference between the\
    highest allocated block in the\
           far\n");
   printf("heap and the top of the far heap\
           is: %lu bytes\n", farcoreleft());
   return 0;
}

函数名: farfree

功 能: 从远堆中释放一块

用 法: void farfree(void);

程序例:

#include <stdio.h>
#include <alloc.h>
#include <string.h>
#include <dos.h>
int main(void)
{
   char far *fptr;
   char *str = "Hello";
   /* allocate memory for the far pointer */
   fptr = farcalloc(10, sizeof(char));
   /* copy "Hello" into allocated memory */
   /*
      Note: movedata is used because you might be in a small data model,
      in which case a normal string copy routine can‘t be used since it
      assumes the pointer size is near.
   */
   movedata(FP_SEG(str), FP_OFF(str),
            FP_SEG(fptr), FP_OFF(fptr),
            strlen(str));
   /* display string (note the F modifier) */
   printf("Far string is: %Fs\n", fptr);
   /* free the memory */
   farfree(fptr);
   return 0;
}

函数名: farmalloc

功 能: 从远堆中分配存储块

用 法: void far *farmalloc(unsigned long size);

程序例:

#include <stdio.h>
#include <alloc.h>
#include <string.h>
#include <dos.h>
int main(void)
{
   char far *fptr;
   char *str = "Hello";
   /* allocate memory for the far pointer */
   fptr = farmalloc(10);
   /* copy "Hello" into allocated memory */
   /*
      Note: movedata is used because we might
      be in a small data model, in which case
      a normal string copy routine can not be
      used since it assumes the pointer size
      is near.
   */
   movedata(FP_SEG(str), FP_OFF(str),
     FP_SEG(fptr), FP_OFF(fptr),
     strlen(str));
   /* display string (note the F modifier) */
   printf("Far string is: %Fs\n", fptr);
   /* free the memory */
   farfree(fptr);
   return 0;
}

函数名: farrealloc

功 能: 调整远堆中的分配块

用 法: void far *farrealloc(void far *block, unsigned long newsize);

程序例:

#include <stdio.h>
#include <alloc.h>
int main(void)
{
   char far *fptr;
   fptr = farmalloc(10);
   printf("First address: %Fp\n", fptr);
   fptr = farrealloc(fptr,20);
   printf("New address  : %Fp\n", fptr);
   farfree(fptr);
   return 0;
}

函数名: fclose

功 能: 关闭一个流

用 法: int fclose(FILE *stream);

程序例:

#include <string.h>
#include <stdio.h>
int main(void)
{
   FILE *fp;
   char buf[11] = "0123456789";
   /* create a file containing 10 bytes */
   fp = fopen("DUMMY.FIL", "w");
   fwrite(&buf, strlen(buf), 1, fp);
   /* close the file */
   fclose(fp);
   return 0;
}

函数名: fcloseall

功 能: 关闭打开流

用 法: int fcloseall(void);

程序例:

#include <stdio.h>
int main(void)
{
   int streams_closed;
   /* open two streams */
   fopen("DUMMY.ONE", "w");
   fopen("DUMMY.TWO", "w");
   /* close the open streams */
   streams_closed = fcloseall();
   if (streams_closed == EOF)
      /* issue an error message */
      perror("Error");
   else
      /* print result of fcloseall() function */
      printf("%d streams were closed.\n", streams_closed);
   return 0;
}

函数名: fcvt

功 能: 把一个浮点数转换为字符串

用 法: char *fcvt(double value, int ndigit, int *decpt, int *sign);

程序例:

#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
int main(void)
{
   char *string;
   double value;
   int dec, sign;
   int ndig = 10;
   clrscr();
   value = 9.876;
   string = ecvt(value, ndig, &dec, &sign);
   printf("string = %s      dec = %d \
          sign = %d\n", string, dec, sign);
   value = -123.45;
   ndig= 15;
   string = ecvt(value,ndig,&dec,&sign);
   printf("string = %s dec = %d sign = %d\n",
          string, dec, sign); 

   value = 0.6789e5; /* scientific
                        notation */
   ndig = 5;
   string = ecvt(value,ndig,&dec,&sign);
   printf("string = %s           dec = %d\
          sign = %d\n", string, dec, sign);
   return 0;
}

函数名: fdopen

功 能: 把流与一个文件句柄相接

用 法: FILE *fdopen(int handle, char *type);

程序例:

#include <sys\stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
   int handle;
   FILE *stream;
   /* open a file */
   handle = open("DUMMY.FIL", O_CREAT,
    S_IREAD | S_IWRITE);
   /* now turn the handle into a stream */
   stream = fdopen(handle, "w");
   if (stream == NULL)
      printf("fdopen failed\n");
   else
   {
      fprintf(stream, "Hello world\n");
      fclose(stream);
   }
   return 0;
}

函数名: feof

功 能: 检测流上的文件结束符

用 法: int feof(FILE *stream);

程序例:

#include <stdio.h>
int main(void)
{
   FILE *stream;
   /* open a file for reading */
   stream = fopen("DUMMY.FIL", "r");
   /* read a character from the file */
   fgetc(stream);
   /* check for EOF */
   if (feof(stream))
      printf("We have reached end-of-file\n");
   /* close the file */
   fclose(stream);
   return 0;
}

函数名: ferror

功 能: 检测流上的错误

用 法: int ferror(FILE *stream);

程序例:

#include <stdio.h>
int main(void)
{
   FILE *stream;
   /* open a file for writing */
   stream = fopen("DUMMY.FIL", "w");
   /* force an error condition by attempting to read */
   (void) getc(stream);
   if (ferror(stream))  /* test for an error on the stream */
   {
      /* display an error message */
      printf("Error reading from DUMMY.FIL\n");
      /* reset the error and EOF indicators */
      clearerr(stream);
   }
   fclose(stream);
   return 0;
}

函数名: fflush

功 能: 清除一个流

用 法: int fflush(FILE *stream);

程序例:

#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <io.h>
void flush(FILE *stream);
int main(void)
{
   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, 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 findfirst(char *pathname, struct ffblk *ffblk, int attrib);

 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 */
   fwrite(msg, strlen(msg)+1, 1, stream);
   /* seek to the beginning of the file */
   fseek(stream, SEEK_SET, 0);
   /* read the data and display it */
   fread(buf, strlen(msg)+1, 1, stream);
   printf("%s\n", buf);
   fclose(stream);
   return 0;
}

函数名: free

功 能: 释放已分配的块

用 法: void free(void *ptr);

程序例:

#include <string.h>
#include <stdio.h>
#include <alloc.h>
int main(void)
{
   char *str;
   /* allocate memory for string */
   str = malloc(10);
   /* copy "Hello" to string */
   strcpy(str, "Hello");
   /* display string */
   printf("String is %s\n", str);
   /* free memory */
   free(str);
   return 0;
}

函数名: freemem

功 能: 释放先前分配的DOS内存块

用 法: int freemem(unsigned seg);

程序例:

#include <dos.h>
#include <alloc.h>
#include <stdio.h>
int main(void)
{
   unsigned int size, segp;
   int stat;
   size = 64; /* (64 x 16) = 1024 bytes */
   stat = allocmem(size, &segp);
   if (stat < 0)
      printf("Allocated memory at segment:\
      %x\n", segp);
   else
      printf("Failed: maximum number of\
      paragraphs available is %u\n",
      stat);
   freemem(segp);
   return 0;
}

函数名: freopen

功 能: 替换一个流

用 法: FILE *freopen(char *filename, char *type, FILE *stream);

程序例:

#include <stdio.h>
int main(void)
{
   /* redirect standard output to a file */
   if (freopen("OUTPUT.FIL", "w", stdout)
       == NULL)
      fprintf(stderr, "error redirecting\
              stdout\n");
   /* this output will go to a file */
   printf("This will go into a file.");
   /* close the standard output stream */
   fclose(stdout);
   return 0;
}

函数名: frexp

功 能: 把一个双精度数分解为尾数的指数

用 法: double frexp(double value, int *eptr);

程序例:

#include <math.h>
#include <stdio.h>
int main(void)
{
   double mantissa, number;
   int exponent;
   number = 8.0;
   mantissa = frexp(number, &exponent);
   printf("The number %lf is ", number);
   printf("%lf times two to the ", mantissa);
   printf("power of %d\n", exponent);
   return 0;
}

函数名: fscanf

功 能: 从一个流中执行格式化输入

用 法: int fscanf(FILE *stream, char *format[,argument...]);

程序例:

#include <stdlib.h>
#include <stdio.h>
int main(void)
{
   int i;
   printf("Input an integer: ");
   /* read an integer from the
      standard input stream */
   if (fscanf(stdin, "%d", &i))
      printf("The integer read was: %i\n",
             i);
   else
   {
      fprintf(stderr, "Error reading an \
              integer from stdin.\n");
      exit(1);
   }
   return 0;
}

函数名: fseek

功 能: 重定位流上的文件指针

用 法: int fseek(FILE *stream, long offset, int fromwhere);

程序例:

#include <stdio.h>
long filesize(FILE *stream);
int main(void)
{
   FILE *stream;
   stream = fopen("MYFILE.TXT", "w+");
   fprintf(stream, "This is a test");
   printf("Filesize of MYFILE.TXT is %ld bytes\n", filesize(stream));
   fclose(stream);
   return 0;
}
long filesize(FILE *stream)
{
   long curpos, length;
   curpos = ftell(stream);
   fseek(stream, 0L, SEEK_END);
   length = ftell(stream);
   fseek(stream, curpos, SEEK_SET);
   return length;
}

函数名: fsetpos

功 能: 定位流上的文件指针

用 法: int fsetpos(FILE *stream, const fpos_t *pos);

程序例:

#include <stdlib.h>
#include <stdio.h>
void showpos(FILE *stream);
int main(void)
{
   FILE *stream;
   fpos_t filepos;
   /* open a file for update */
   stream = fopen("DUMMY.FIL", "w+");
   /* save the file pointer position */
   fgetpos(stream, &filepos);
   /* write some data to the file */
   fprintf(stream, "This is a test");
   /* show the current file position */
   showpos(stream);
   /* set a new file position, display it */
   if (fsetpos(stream, &filepos) == 0)
     showpos(stream);
   else
   {
      fprintf(stderr, "Error setting file \
       pointer.\n");
      exit(1);
   }
   /* close the file */
   fclose(stream);
   return 0;
}
void showpos(FILE *stream)
{
   fpos_t pos;
   /* display the current file pointer
      position of a stream */
   fgetpos(stream, &pos);
   printf("File position: %ld\n", pos);
}

函数名: fstat

功 能: 获取打开文件信息

用 法: int fstat(char *handle, struct stat *buff);

程序例:

#include <sys\stat.h>
#include <stdio.h>
#include <time.h>
int main(void)
{
   struct stat statbuf;
   FILE *stream;
   /* open a file for update */
   if ((stream = fopen("DUMMY.FIL", "w+"))
       == NULL)
   {
      fprintf(stderr, "Cannot open output \
              file.\n");
      return(1);
   }
   fprintf(stream, "This is a test");
   fflush(stream);
   /* get information about the file */
   fstat(fileno(stream), &statbuf);
   fclose(stream);
   /* display the information returned */
   if (statbuf.st_mode & S_IFCHR)
      printf("Handle refers to a device.\n");
   if (statbuf.st_mode & S_IFREG)
      printf("Handle refers to an ordinary \
             file.\n");
   if (statbuf.st_mode & S_IREAD)
      printf("User has read permission on \
             file.\n");
   if (statbuf.st_mode & S_IWRITE)
      printf("User has write permission on \
              file.\n");
   printf("Drive letter of file: %c\n",
   ‘A‘+statbuf.st_dev);
   printf("Size of file in bytes: %ld\n",
   statbuf.st_size);
   printf("Time file last opened: %s\n",
   ctime(&statbuf.st_ctime));
   return 0;
}

函数名: ftell

功 能: 返回当前文件指针

用 法: long ftell(FILE *stream);

程序例:

#include <stdio.h>
int main(void)
{
   FILE *stream;
   stream = fopen("MYFILE.TXT", "w+");
   fprintf(stream, "This is a test");
   printf("The file pointer is at byte \
          %ld\n", ftell(stream));
   fclose(stream);
   return 0;
}

函数名: fwrite

功 能: 写内容到流中

用 法: int fwrite(void *ptr, int size, int nitems, FILE *stream);

程序例:

#include <stdio.h>
struct mystruct
{
  int i;
  char ch;
};
int main(void)
{
   FILE *stream;
   struct mystruct s;
   if ((stream = fopen("TEST.$$$", "wb")) == NULL) /* open file TEST.$$$ */
   {
      fprintf(stderr, "Cannot open output file.\n");
      return 1;
   }
   s.i = 0;
   s.ch = ‘A‘;
   fwrite(&s, sizeof(s), 1, stream); /* write struct s to file */
   fclose(stream); /* close file */
   return 0;
}

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