C语言函数-L开头_C语言教程

C语言函数-L开头_C语言教程

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;
}

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