wdg_022l.txt

c编程宝典,详细介绍有关c的资料

函数名: labs 
功  能: 取长整型绝对值 
用  法: long labs(long n); 
程序例: 

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
   long result; 
   long x = -12345678L; 

   result= labs(x); 
   printf("number: %ld abs value: %ld\n", 
      x, result); 

   return 0; 
} 
  
  
  

函数名: ldexp 
功  能: 计算value*2的幂 
用  法: double ldexp(double value, int exp); 
程序例: 

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
   double value; 
   double x = 2; 

   /* ldexp raises 2 by a power of 3 
      then multiplies the result by 2   */ 
   value = ldexp(x,3); 
   printf("The ldexp value is: %lf\n", 
      value); 

   return 0; 
} 
  
  

函数名: ldiv 
功  能: 两个长整型数相除, 返回商和余数 
用  法: ldiv_t ldiv(long lnumer, long ldenom); 
程序例: 

/* ldiv example */ 

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

int main(void) 
{ 
   ldiv_t lx; 

   lx = ldiv(100000L, 30000L); 
   printf("100000 div 30000 = %ld remainder %ld\n", lx.quot, lx.rem); 
   return 0; 
} 
  
  
  

函数名: lfind 
功  能: 执行线性搜索 
用  法: void *lfind(void *key, void *base, int *nelem, int width, 
      int (*fcmp)()); 
程序例: 

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

int compare(int *x, int *y) 
{ 
   return( *x - *y ); 
} 

int main(void) 
{ 
   int array[5] = {35, 87, 46, 99, 12}; 
   size_t nelem = 5; 
   int key; 
   int *result; 

   key = 99; 
   result = lfind(&key, array, &nelem, 
        sizeof(int), (int(*)(const void *,const void *))compare); 
   if (result) 
      printf("Number %d found\n",key); 
   else 
      printf("Number %d not found\n",key); 

   return 0; 
} 
  
  

函数名: line 
功  能: 在指定两点间画一直线 
用  法: void far line(int x0, int y0, int x1, int y1); 
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 xmax, ymax; 

   /* initialize graphics and local variables */ 
   initgraph(&gdriver, &gmode, ""); 

   /* read result of initialization */ 
   errorcode = graphresult(); 
   /* an error occurred */ 
   if (errorcode != grOk) 
   { 
      printf("Graphics error: %s\n", 
             grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); 
   } 

   setcolor(getmaxcolor()); 
   xmax = getmaxx(); 
   ymax = getmaxy(); 

   /* draw a diagonal line */ 
   line(0, 0, xmax, ymax); 

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

函数名: linerel 
功  能: 从当前位置点(CP)到与CP有一给定相对距离的点画一直线 
用  法: void far linerel(int dx, int dy); 
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; 
   char msg[80]; 

   /* initialize graphics and local variables */ 
   initgraph(&gdriver, &gmode, ""); 

   /* read result of initialization */ 
   errorcode = graphresult(); 
   if (errorcode != grOk) 
   { 
      printf("Graphics error: %s\n", 
  grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); 
   } 

   /* move the C.P. to location (20, 30) */ 
   moveto(20, 30); 

   /* create and output a 
      message at (20, 30) */ 
   sprintf(msg, " (%d, %d)", getx(), gety()); 
   outtextxy(20, 30, msg); 

   /* draw a line to a point a relative 
      distance away from the current 
      value of C.P.   */ 
   linerel(100, 100); 

   /* create and output a message at C.P. */ 
   sprintf(msg, " (%d, %d)", getx(), gety()); 
   outtext(msg); 

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

函数名: localtime 
功  能: 把日期和时间转变为结构 
用  法: struct tm *localtime(long *clock); 
程序例: 

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

int main(void) 
{ 
   time_t timer; 
   struct tm *tblock; 

   /* gets time of day */ 
   timer = time(NULL); 

   /* converts date/time to a structure */ 
   tblock = localtime(&timer); 

   printf("Local time is: %s", asctime(tblock)); 

   return 0; 
} 
  
  
  

函数名: lock 
功  能: 设置文件共享锁 
用  法: int lock(int handle, long offset, long length); 
程序例: 

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

int main(void) 
{ 
   int handle, status; 
   long length; 

   /* Must have DOS Share.exe loaded for */ 
   /* file locking to function properly */ 

   handle = sopen("c:\\autoexec.bat", 
      O_RDONLY,SH_DENYNO,S_IREAD); 

   if (handle < 0) 
   { 
      printf("sopen failed\n"); 
      exit(1); 
   } 

   length = filelength(handle); 
   status = lock(handle,0L,length/2); 

   if (status == 0) 
      printf("lock succeeded\n"); 
   else 
      printf("lock failed\n"); 

   status = unlock(handle,0L,length/2); 

   if (status == 0) 
      printf("unlock succeeded\n"); 
   else 
      printf("unlock failed\n"); 

   close(handle); 
   return 0; 
} 
  
  

函数名: log 
功  能: 对数函数ln(x) 
用  法: double log(double x); 
程序例: 

#include <math.h> 
#include <stdio.h> 

int main(void) 
{ 
   double result; 
   double x = 8.6872; 

   result = log(x); 
   printf("The natural log of %lf is %lf\n", x, result); 

   return 0; 
} 
  
  

函数名: log10 
功  能: 对数函数log 
用  法: double log10(double x); 
程序例: 

#include <math.h> 
#include <stdio.h> 

int main(void) 
{ 
   double result; 
   double x = 800.6872; 

   result = log10(x); 
   printf("The common log of %lf is %lf\n", x, result); 

   return 0; 
} 
  
  
  

函数名: longjump 
功  能: 执行非局部转移 
用  法: void longjump(jmp_buf env, int val); 
程序例: 

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

void subroutine(jmp_buf); 

int main(void) 
{ 

   int value; 
   jmp_buf jumper; 

   value = setjmp(jumper); 
   if (value != 0) 
   { 
      printf("Longjmp with value %d\n", value); 
      exit(value); 
   } 
   printf("About to call subroutine ... \n"); 
   subroutine(jumper); 

   return 0; 
} 

void subroutine(jmp_buf jumper) 
{ 
   longjmp(jumper,1); 
} 
  
  
  

函数名: lowvideo 
功  能: 选择低亮度字符 
用  法: void lowvideo(void); 
程序例: 

#include <conio.h> 

int main(void) 
{ 
   clrscr(); 

   highvideo(); 
   cprintf("High Intesity Text\r\n"); 
   lowvideo(); 
   gotoxy(1,2); 
   cprintf("Low Intensity Text\r\n"); 

   return 0; 
} 
  
  
  

函数名: lrotl, _lrotl 
功  能: 将无符号长整型数向左循环移位 
用  法: unsigned long lrotl(unsigned long lvalue, int count); 
 unsigned long _lrotl(unsigned long lvalue, int count); 
程序例: 

/* lrotl example */ 
#include <stdlib.h> 
#include <stdio.h> 

int main(void) 
{ 
   unsigned long result; 
   unsigned long value = 100; 

   result = _lrotl(value,1); 
   printf("The value %lu rotated left one bit is: %lu\n", value, result); 

   return 0; 
} 
  
  

函数名: lsearch 
功  能: 线性搜索 
用  法: void *lsearch(const void *key, void *base, size_t *nelem, 
       size_t width, int (*fcmp)(const void *, const void *)); 
程序例: 

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

int compare(int *x, int *y) 
{ 
   return( *x - *y ); 
} 

int main(void) 
{ 
   int array[5] = {35, 87, 46, 99, 12}; 
   size_t nelem = 5; 
   int key; 
   int *result; 

   key = 99; 
   result = lfind(&key, array, &nelem, 
               sizeof(int), (int(*)(const void *,const void *))compare); 
   if (result) 
      printf("Number %d found\n",key); 
   else 
      printf("Number %d not found\n",key); 

   return 0; 
} 
  
  
  

函数名: lseek 
功  能: 移动文件读/写指针 
用  法: long lseek(int handle, long offset, int fromwhere); 
程序例: 

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

int main(void) 
{ 
   int handle; 
   char msg[] = "This is a test"; 
   char ch; 

   /* create a file */ 
   handle = open("TEST.$$$", O_CREAT | O_RDWR, S_IREAD | S_IWRITE); 

   /* write some data to the file */ 
   write(handle, msg, strlen(msg)); 

   /* seek to the begining of the file */ 
   lseek(handle, 0L, SEEK_SET); 

   /* reads chars from the file until we hit EOF */ 
   do 
   { 
      read(handle, &ch, 1); 
      printf("%c", ch); 
   }  while (!eof(handle)); 

   close(handle); 
   return 0; 
}