[c函数之f].txt

C常用函数 多了解一些有好处的

/* 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); /* di