Solved

File handling

Posted on 2002-03-13
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Last Modified: 2012-05-07
I have problems handling file:

1) Look at this piece of code :

while(!feof(filepointer)
{

   fscanf(filepointer,"%s",name);
}

File has 5 name like this :
name1
name2
name3
name4
name5

This while loop reads till name4. then reads name5.
Now, it should stop here.
But it goes and reads name 5 again and then comes out.
I do not understand how.

2)In my program I am writing some thing into a file.
while this process is going on, I am not able to see anything written to the file using VI editor.
I am doing fflush() soon after I write to the file.
Please help
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Question by:kgreddy
8 Comments
 
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Accepted Solution

by:
Triskelion earned 50 total points
ID: 6860422
The problem is that you do not get the determination of eof() until after the next fscanf().

Try something BRUTAL like this

while (!feof(filepointer))
{
   fscanf(filepointer, "%s", strSomeTempString);
   if (!feof(filepointer))
      {
      //copy to target string
      }
}

or

use gets()
since you're just dealing with one string
 
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Expert Comment

by:Triskelion
ID: 6860424
make that fgets()
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LVL 6

Expert Comment

by:Triskelion
ID: 6860452
This works as expected:

#include <stdio.h>

int main(void)
{
     FILE * hanInFile=NULL;
     char     strData[16] = {0};
     if (NULL == (hanInFile=fopen("..\\20276268.txt", "rb")))
          {
          puts ("cannot open input file");
          return 1;
          }

     while (!feof(hanInFile))
          {
          fgets(strData, sizeof(strData), hanInFile);
          puts(strData);
          }
     fclose(hanInFile);
     return 0;
}
0
 
LVL 6

Expert Comment

by:Triskelion
ID: 6860469
...but then again, so does this:
#include <stdio.h>

int main(void)
{
     FILE * hanInFile=NULL;
     char     strData[16] = {0};
     if (NULL == (hanInFile=fopen("..\\20276268.txt", "r")))
          {
          puts ("cannot open input file");
          return 1;
          }

     while (!feof(hanInFile))
          {
          /*fgets(strData, sizeof(strData), hanInFile);*/
          fscanf(hanInFile, "%s", strData);
          puts(strData);
          }
     fclose(hanInFile);
     return 0;
}
/*
Hmmm...
Are you sure you don't have trailing spaces or an end-of-file marker floating around somewhere?
*/
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Expert Comment

by:Shivshankar
ID: 6867345
I see a simple solution.
     FILE * fp;
     .
     .
     .
     fscanf(fp, "%s", name);
     while(!feof(fp)) {
          printf("%s\n", name);
          fscanf(fp, "%s", name);
     }

This works fine in all the 3 compilers I have.
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Expert Comment

by:Triskelion
ID: 6888434
kgreddy, have you tried any of these?
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by:Moondancer
ID: 6892774
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