A question about file pointers in Linux?

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);
Ranch
   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. Excuse me, what went wrong there, I have been looking for a long time and still have no clue.

starwr

Did you make the second call there

rellor

Is the file not closed yet? Calling it in main after the call is complete will risk the mistake you said

avenli

The problem lies in your strncpy, this function in linux will initialize dest with 0, the length is the third parameter of strncpy, and the parameter you give is obviously larger than the size of dest, so unpredictable things happen ...