c函数之r.txt

C常用函数 多了解一些有好处的

 函数名: raise 
功 能: 向正在执行的程序发送一个信号 
用 法: int raise(int sig); 
程序例: 

#include <signal.h> 

int main(void) 
{ 
int a, b; 

a = 10; 
b = 0; 
if (b == 0) 
/* preempt divide by zero error */ 
raise(SIGFPE); 
a = a / b; 
return 0; 
} 



函数名: rand 
功 能: 随机数发生器 
用 法: void rand(void); 
程序例: 

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

int main(void) 
{ 
int i; 

printf("Ten random numbers from 0 to 99\n\n"); 
for(i=0; i<10; i++) 
printf("%d\n", rand() % 100); 
return 0; 
} 



函数名: randbrd 
功 能: 随机块读 
用 法: int randbrd(struct fcb *fcbptr, int reccnt); 
程序例: 

#include <process.h> 
#include <string.h> 
#include <stdio.h> 
#include <dos.h> 

int main(void) 
{ 
char far *save_dta; 
char line[80], buffer[256]; 
struct fcb blk; 
int i, result; 

/* get user input file name for dta */ 
printf("Enter drive and file name (no path - i.e. a:file.dat)\n"); 
gets(line); 

/* put file name in fcb */ 
if (!parsfnm(line, &blk, 1)) 
{ 
printf("Error in call to parsfnm\n"); 
exit(1); 
} 
printf("Drive #%d File: %s\n\n", blk.fcb_drive, blk.fcb_name); 

/* open file with DOS FCB open file */ 
bdosptr(0x0F, &blk, 0); 

/* save old dta, and set new one */ 
save_dta = getdta(); 
setdta(buffer); 

/* set up info for the new dta */ 
blk.fcb_recsize = 128; 
blk.fcb_random = 0L; 
result = randbrd(&blk, 1); 

/* check results from randbrd */ 
if (!result) 
printf("Read OK\n\n"); 
else 
{ 
perror("Error during read"); 
exit(1); 
} 

/* read in data from the new dta */ 
printf("The first 128 characters are:\n"); 
for (i=0; i<128; i++) 
putchar(buffer[i]); 

/* restore previous dta */ 
setdta(save_dta); 

return 0; 
} 


函数名: randbwr 
功 能: 随机块写 
用 法: int randbwr(struct fcp *fcbptr, int reccnt); 
程序例: 

#include <process.h> 
#include <string.h> 
#include <stdio.h> 
#include <dos.h> 

int main(void) 
{ 
char far *save_dta; 
char line[80]; 
char buffer[256] = "RANDBWR test!"; 
struct fcb blk; 
int result; 

/* get new file name from user */ 
printf("Enter a file name to create (no path - ie. a:file.dat\n"); 
gets(line); 

/* parse the new file name to the dta */ 
parsfnm(line,&blk,1); 
printf("Drive #%d File: %s\n", blk.fcb_drive, blk.fcb_name); 

/* request DOS services to create file */ 
if (bdosptr(0x16, &blk, 0) == -1) 
{ 
perror("Error creating file"); 
exit(1); 
} 

/* save old dta and set new dta */ 
save_dta = getdta(); 
setdta(buffer); 

/* write new records */ 
blk.fcb_recsize = 256; 
blk.fcb_random = 0L; 
result = randbwr(&blk, 1); 

if (!result) 
printf("Write OK\n"); 
else 
{ 
perror("Disk error"); 
exit(1); 
} 

/* request DOS services to close the file */ 
if (bdosptr(0x10, &blk, 0) == -1) 
{ 
perror("Error closing file"); 
exit(1); 
} 

/* reset the old dta */ 
setdta(save_dta); 

return 0; 
} 



函数名: random 
功 能: 随机数发生器 
用 法: int random(int num); 
程序例: 

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

/* prints a random number in the range 0 to 99 */ 
int main(void) 
{ 
randomize(); 
printf("Random number in the 0-99 range: %d\n", random (100)); 
return 0; 
} 



函数名: randomize 
功 能: 初始化随机数发生器 
用 法: void randomize(void); 
程序例: 

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

int main(void) 
{ 
int i; 

randomize(); 
printf("Ten random numbers from 0 to 99\n\n"); 
for(i=0; i<10; i++) 
printf("%d\n", rand() % 100); 
return 0; 
} 



函数名: read 
功 能: 从文件中读 
用 法: int read(int handle, void *buf, int nbyte); 
程序例: 

#include <stdio.h> 
#include <io.h> 
#include <alloc.h> 
#include <fcntl.h> 
#include <process.h> 
#include <sys\stat.h> 

int main(void) 
{ 
void *buf; 
int handle, bytes; 

buf = malloc(10); 

/* 
Looks for a file in the current directory named TEST.$$$ and attempts 
to read 10 bytes from it. To use this example you should create the 
file TEST.$$$ 
*/ 
if ((handle = 
open("TEST.$$$", O_RDONLY | O_BINARY, S_IWRITE | S_IREAD)) == -1) 
{ 
printf("Error Opening File\n"); 
exit(1); 
} 

if ((bytes = read(handle, buf, 10)) == -1) { 
printf("Read Failed.\n"); 
exit(1); 
} 
else { 
printf("Read: %d bytes read.\n", bytes); 
} 
return 0; 
} 



函数名: realloc 
功 能: 重新分配主存 
用 法: void *realloc(void *ptr, unsigned newsize); 
程序例: 

#include <stdio.h> 
#include <alloc.h> 
#include <string.h> 

int main(void) 
{ 
char *str; 

/* allocate memory for string */ 
str = malloc(10); 

/* copy "Hello" into string */ 
strcpy(str, "Hello"); 

printf("String is %s\n Address is %p\n", str, str); 
str = realloc(str, 20); 
printf("String is %s\n New address is %p\n", str, str); 

/* free memory */ 
free(str); 

return 0; 
} 



函数名: rectangle 
功 能: 画一个矩形 
用 法: void far rectangle(int left, int top, int right, int bottom); 
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 left, top, right, bottom; 

/* initialize graphics and 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 */ 
} 

left = getmaxx() / 2 - 50; 
top = getmaxy() / 2 - 50; 
right = getmaxx() / 2 + 50; 
bottom = getmaxy() / 2 + 50; 

/* draw a rectangle */ 
rectangle(left,top,right,bottom); 

/* clean up */ 
getch(); 
closegraph(); 
return 0; 
} 



函数名: registerbgidriver 
功 能: 登录已连接进来的图形驱动程序代码 
用 法: int registerbgidriver(void(*driver)(void)); 
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; 

/* register a driver that was added into graphics.lib */ 
errorcode = registerbgidriver(EGAVGA_driver); 

/* report any registration errors */ 
if (errorcode < 0) 
{ 
printf("Graphics error: %s\n", grapherrormsg(errorcode)); 
printf("Press any key to halt:"); 
getch(); 
exit(1); /* terminate with an error code */ 
} 

/* initialize graphics and 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 */ 
} 

/* draw a line */ 
line(0, 0, getmaxx(), getmaxy()); 

/* clean up */ 
getch(); 
closegraph(); 
return 0; 
} 



函数名: remove 
功 能: 删除一个文件 
用 法: int remove(char *filename); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
char file[80]; 

/* prompt for file name to delete */ 
printf("File to delete: "); 
gets(file); 

/* delete the file */ 
if (remove(file) == 0) 
printf("Removed %s.\n",file); 
else 
perror("remove"); 

return 0; 
} 



函数名: rename 
功 能: 重命名文件 
用 法: int rename(char *oldname, char *newname); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
char oldname[80], newname[80]; 

/* prompt for file to rename and new name */ 
printf("File to rename: "); 
gets(oldname); 
printf("New name: "); 
gets(newname); 

/* Rename the file */ 
if (rename(oldname, newname) == 0) 
printf("Renamed %s to %s.\n", oldname, newname); 
else 
perror("rename"); 

return 0; 
} 



函数名: restorecrtmode 
功 能: 将屏幕模式恢复为先前的imitgraph设置 
用 法: void far restorecrtmode(void); 
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 x, y; 

/* initialize graphics and 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 */ 
} 

x = getmaxx() / 2; 
y = getmaxy() / 2; 

/* output a message */ 
settextjustify(CENTER_TEXT, CENTER_TEXT); 
outtextxy(x, y, "Press any key to exit graphics:"); 
getch(); 

/* restore system to text mode */ 
restorecrtmode(); 
printf("We're now in text mode.\n"); 
printf("Press any key to return to graphics mode:"); 
getch(); 

/* return to graphics mode */ 
setgraphmode(getgraphmode()); 

/* output a message */ 
settextjustify(CENTER_TEXT, CENTER_TEXT); 
outtextxy(x, y, "We're back in graphics mode."); 
outtextxy(x, y+textheight("W"), "Press any key to halt:"); 

/* clean up */ 
getch(); 
closegraph(); 
return 0; 
} 



函数名: rewind 
功 能: 将文件指针重新指向一个流的开头 
用 法: int rewind(FILE *stream); 
程序例: 

#include <stdio.h> 
#include <dir.h> 

int main(void) 
{ 
FILE *fp; 
char *fname = "TXXXXXX", *newname, first; 

newname = mktemp(fname); 
fp = fopen(newname,"w+"); 
fprintf(fp,"abcdefghijklmnopqrstuvwxyz"); 
rewind(fp); 
fscanf(fp,"%c",&first); 
printf("The first character is: %c\n",first); 
fclose(fp); 
remove(newname); 

return 0; 
} 



函数名: rmdir 
功 能: 删除DOS文件目录 
用 法: int rmdir(char *stream); 
程序例: 

#include <stdio.h> 
#include <conio.h> 
#include <process.h> 
#include <dir.h> 

#define DIRNAME "testdir.$$$" 

int main(void) 
{ 
int stat; 

stat = mkdir(DIRNAME); 
if (!stat) 
printf("Directory created\n"); 
else 
{ 
printf("Unable to create directory\n"); 
exit(1); 
} 

getch(); 
system("dir/p"); 
getch(); 

stat = rmdir(DIRNAME); 
if (!stat) 
printf("\nDirectory deleted\n"); 
else 
{ 
perror("\nUnable to delete directory\n"); 
exit(1); 
} 

return 0; 
} 




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