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Turbo C 2.0、Borland C++库函数及用例(33) }
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>
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