C语言的函数!

内财数模协会 · 发表于 2004-5-8 17:38:53

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:39:03

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:39:11

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:39:23

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:39:33

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:39:45

<

>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);
}

内财数模协会 · 发表于 2004-5-8 17:39:54

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:40:03

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:40:15

<

>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;
}

内财数模协会 · 发表于 2004-5-8 17:41:03

<

>函数名: gcvt
功能: 把浮点数转换成字符串
用法: char *gcvt(double value, int ndigit, char *buf);
程序例: <

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

>int main(void)
{
char str[25];
double num;
int sig = 5; /* significant digits */ /* a regular number */
num = 9.876;
gcvt(num, sig, str);
printf("string = %s\n", str); /* a negative number */
num = -123.4567;
gcvt(num, sig, str);
printf("string = %s\n", str); /* scientific notation */
num = 0.678e5;
gcvt(num, sig, str);
printf("string = %s\n", str); return(0);
}

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