C语言库函数(R类字母)

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; 
}