How to create and remove a unix soft link

A soft link, or more common, a symlink, is link a shortcut to the targeted file or directory. So when is removed the original target stays present.

A symlink can be created like:

ln -s /path/ linkname

from the ln man pages:

ln [OPTION]… [-T] TARGET LINK_NAME (1st form)

-s, –symbolic
make symbolic links instead of hard links

to remove a symlink

rm linkname

You can't update the soft link to point to other target path, you must delete the soft link first and recreate it

C preprocessor use for replace string by '##'

C preprocessor allow us to replace string by putting '##' on variable

eg.

#include "stdio.h"

void func_replace(){printf("func_replace is called\n");}

#define REPLACE_FUNC(A) func_##A()

void main()
{
/*func_replace will be invoked*/
REPLACE_FUNC(replace);
}

SS7 point code converter

There are plenty of ss7 web base point code converter on web, but i can't find a open source version of point code converter. I had built a command line point code converter for my own used. here i share it out. :)

#include "stdio.h"
#include "string.h"

int main()
{
 char buffer[200];
 int point_code;
 int point_code1,point_code2,point_code3;
 int convertion_type;
 while(1)
 {
   printf("please enter converted format \n"
     "0 - quit \n"
     "1 - [3-8-3] -> hex \n"
     "2 - [8-8-8] -> hex \n"
     "3 - hex -> [3-8-3] \n"
     "4 - hex -> [8-8-8] \n");

   gets(buffer);
   sscanf(buffer,"%d",&convertion_type);

   if(buffer[0]=='q')
   {
     printf("app exit\n");
   }
   switch(convertion_type)
   {
   case 1:
     //eq - 0x2044
     //0010000001000100
     //--100 00001000 100
     //4-8-4
     printf("enter your point code [3-8-3]\n");
     gets(buffer);
     sscanf(buffer,"%d-%d-%d",
       &point_code1,&point_code2,&point_code3);
     point_code = (point_code1<<11) point_code =" %x\n" point_code =" (point_code1<<16)" point_code =" %x\n" point_code1 =" (point_code">>11)&0x00000007;
     point_code2 = (point_code>>3)&0x000000ff;
     point_code3 = (point_code)&0x00000007;
     printf("point_code = %d-%d-%d\n",point_code1,point_code2,point_code3);
     break;
   case 4:
     printf("enter your point code [Hex]\n");
     gets(buffer);
     sscanf(buffer,"%x",&point_code);
     point_code1 = (point_code>>16)&0x000000ff;
     point_code2 = (point_code>>8)&0x000000ff;
     point_code3 = (point_code)&0x000000ff;
     printf("point_code = %d-%d-%d\n",point_code1,point_code2,point_code3);
     break;
   }
 }
 return 0;
}

precompiled version of point code converter can be downloaded here
pc_convertor