empty file string manipulation

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September 25th, 2002, 02:51 PM

nur

Junior Member

Join Date: Sep 2002

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empty file string manipulation

am doing some string manipulation on a file:

the file has all sorts of characters strings, including newline i.e
content of the file contents - video.reg is as follows:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Hardware
Profiles\Current\System\CurrentControlSet\SERVICES
\ATIRAGE3]

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Hardware
Profiles\Current\System\CurrentControlSet\SERVICES
\ATIRAGE3\DEVICE0]

"DefaultSettings.YResolution"=dword:00000258
"DefaultSettings.VRefresh"=dword:0000004b
"DefaultSettings.Flags"=dword:00000000
"DefaultSettings.XPanning"=dword:00000000
"DefaultSettings.YPanning"=dword:00000000

..............

The problem is i want to replace the occurance of
"DefaultSettings.VRefresh"=dword:0000003B
or
("DefaultSettings.VRefresh"=dword:0000004B)
with
"DefaultSettings.VRefresh"=dword:0000004C and save the changes to the
same file or different file

This is the code i have written so far but doesnt work

#include <stdio.h>
#include <errno.h> /* for strerror() */
#include <string.h>
#include <stdlib.h>

int main(void)
{

FILE *fp, *tmp;

if ((fp=fopen("C:\\video.reg","r"))==NULL){
/* error */
}

if ((tmp=fopen("C:\\ob.reg","w+"))==NULL){
/* error */
printf("error videob");

}

else{

char line[256];

while( ! feof(fp) ) {
fgets(line, sizeof(line), fp);

{
char *ptr;
while ((ptr = strstr (line,
"\"DefaultSettings.VRefresh\"=dword:0000004b")) != NULL) {
strcpy (ptr, "DefaultSettings.VRefresh\"=dword:0000004c");
}
}

fputs(ptr, tmp);
}

}

return 0;

fclose(tmp);

fclose(fp);

This doesnt work, it produces an empty file!!

Thank you all in advance..

September 25th, 2002, 05:49 PM

Scorpions4ever

Banned ;)

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Join Date: Nov 2001

Location: Glendale, Los Angeles County, California, USA

Posts: 7,442

Time spent in forums: 1 Month 1 h 55 m 33 sec
Reputation Power: 797

How about something like this:

Code:

#include <stdio.h>
#include <errno.h> /* for strerror() */
#include <string.h>
#include <stdlib.h>

int main(void)
{
    FILE *fp, *tmp;

    if ((fp=fopen("C:\\video.reg","r"))==NULL){ 
       /* error */ 
    } 


     if ((tmp=fopen("C:\\ob.reg","w+"))==NULL){ 
         /* error */ 
         printf("error videob"); 
     } else{
          char line[256];
          while( ! feof(fp) ) {
               fgets(line, sizeof(line), fp);
              {
                 if (strstr (line,
                          "\"DefaultSettings.VRefresh\"=dword:0000004b")                             != NULL) 
                      strcpy (line, "DefaultSettings.VRefresh\"=dword:0000004c");
                  
              }

              fputs(line, tmp);
          }
      }

       fclose(tmp);
       fclose(fp);
       return 0;
}

Your main error is where you used fputs (ptr, tmp); The problem is that if line does not contain "DefaultSettings.VRefresh...", then ptr will be NULL. If the line did contain "DefaultSettings.VRefresh", you were copying a new line over. However, since you had your strstr function in a while loop, so it would check the line again (which now contains the new data) and would set ptr to NULL again. That's why you ended up with an empty file. Also you had a return 0 before you closed your files, which I moved.

I fixed the code above off the top of my head, so I won't guarantee that it'll compile, but I hope this helps!

September 26th, 2002, 07:55 PM

Optix

Contributing User

Join Date: Jun 2002

Posts: 36

Time spent in forums: < 1 sec
Reputation Power: 7

lol u know too much scorpian

j/p

btw how old are you?

September 27th, 2002, 03:11 AM