Ask a question about pointers.

changyl123

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

int Get_Config (char * lpFileName, char * SerchBuf, char * szTmp)
{
    FILE * stream;
    char pBuf [256] = "";
    char * p;
    char * ptoken = NULL;
    
   if ((stream = fopen (lpFileName, "rt")) == NULL)
  {
printf ("opne file is error\n");
        return -1;
  }
while (! feof (stream))
{
memset (pBuf, 0x00, 256);
fgets (pBuf, 256, stream);
if (strstr (pBuf, SerchBuf))
{
p = strchr (pBuf, '=');
strncpy (szTmp, p + 1, sizeof (pBuf));
printf ("this is very important data% s\n", szTmp);
break;
}
else
continue;
    }
    fclose (stream);
    return 1;
}


int main ()
{
    char lpFileName [128] = "Config.ini";
    char szTmp [128];
    
    memset (szTmp, 0x00, 128);
    if (Get_Config (lpFileName, "TMP_LEN =", szTmp) ==-1)
    {
       printf ("get config error\n");
    }
    printf ("this TMP_LEN is% s\n", szTmp);

   getchar ();
    return 0;
}

When I execute this program, I can correctly read the contents of the configuration file once, but the second time I call the Get_Config function above, the lpFileName file cannot be opened normally. In this case, it appears as opne file is error. Excuse me, prawns?

yexilove

After opening the file, turn it off.
fclose (stream);

changyl123

I added this line to my code.
However, it can only be executed once, and the file cannot be opened when called again.

gogoandsoso

strncpy (szTmp, p + 1, sizeof (pBuf));
-------------------------------------
The problem with this line, szTmp you only defined the size of 128 bytes, copy used sizeof (pBuf) = 256, resulting in out-of-bounds operation, the file name area is overwritten, no file name, of course, the second time can not open the file .

gogoandsoso

strncpy (szTmp, p + 1, sizeof (pBuf));
--------------------------
There is a problem with this line, sizeof (pBuf) = 256, and your szTmp is only 128 bytes in size, resulting in an out-of-bounds operation, overwriting the contents of lpFileName. When the function is called again, there is no file name, and of course there is an error opening the file.

gogoandsoso

strncpy (szTmp, p + 1, sizeof (pBuf));
Cross-border operation, washed the file name

gogoandsoso

strncpy (szTmp, p + 1, sizeof (pBuf));
Out of bounds operation, the file name was overwritten, and an error occurred when opening again.

gogoandsoso

strncpy (szTmp, p + 1, sizeof (pBuf));
Cross-border operation, overwriting the file name.

qingclie

Unlikely

gogoandsoso

strncpy (szTmp, p + 1, sizeof (pBuf));
There is something wrong with this line of code. The file name is overwritten.