Thread: writing what a program has read

I have been able to read what are the contents of a file and display them on the screen, it worked well

Then i tried to write a new file (file1.dat) that contains the odd lines of the first file. But there is nothing that appears on file1.dat.

Code:

  FILE * fp, * outptr;
  char lines [ 90 ];

  if ( ( fp = fopen ( FILENAME, "r" ) ) == NULL ) {
    fprintf ( stderr, "fileloop1: Unable to open %s!\n", FILENAME );
    exit ( 1 );
    }

  fgets (lines, 90, fp);

  while ( ! feof ( fp ) ) 
  {
     fputs ( lines, stdout ); 
     fgets ( lines, 90, fp ); //displaying the contents of a file 
   }

     if(feof(fp))
     {
        fgets(lines, 90, fp);
        outptr = fopen ("file1.dat","w");
        fprintf(outptr, "%s\n", lines); // trying to write the line of the first file in the second one
       }

please help

thanks for your reply

well, I changed the code a bit

Code:

  while ( ! feof ( fp ) ) {
    outptr = fopen ("file1.dat","w");
    fputs ( buffer, stdout );
    fgets ( buffer, 81, fp );
    fprintf(outptr, "%s\n", buffer);
    }

now, "file1.dat" shows some output, but it's the last line of the file and it misses the first 2 letters... what's happening ?

Originally Posted by Salem

while ( fgets( buff, sizeof buff, fp ) != NULL ) fputs( buff, stdout );

Is all you need to copy a text file to your terminal.

thanks but it's not what I all need.

copying a file to a terminal, i've already been able to do it.

but how about writing a new file that writes what the program has read ?

Code:

while ( fgets( buffer, sizeof buffer, fp ) != NULL ) fputs( buffer, stdout );  {
    outptr = fopen ("file1.dat","w");
    fprintf(outptr, "%s", buffer);
    }

Why the file file1.dat is empty after every run of the program. Where did I mistake ?

Where did you see any problem with the identation of these 4 lines of code ??

Code:

while ( fgets( buffer, sizeof buffer, fp ) != NULL ) fputs( buffer, stdout );  {
    outptr = fopen ("file1.dat","w");
    fprintf(outptr, "%s", buffer);
    }

Originally Posted by Dave_Sinkula

Where's the loop body? And even if your loop body was correct, why continually reopen and truncate the file?

No it's not what i am trying to do, there are 2 files, the first one is file.dat the second is file1.dat

File.dat has a list of 10 lines.

When I do this:

Code:

while ( fgets( buffer, sizeof buffer, fp ) != NULL ) {
    fputs( buffer, stdout );
    outptr = fopen ("file1.dat","w");   // opening and creating  a new file
    fprintf(outptr, "%s", buffer);  // write in it lines of the first file
    }

its output is the last line of the output, and it misses the first 2 letters, I don't know what to change in order to fix that.

Code:

 
  FILE * fp, * outptr, * outptr2;
  char buffer [ 81 ];
  int i;
  outptr = fopen ("file1.dat","w"); 
  outptr2 = fopen ("file2.dat","w");
 
  if ( ( fp = fopen ( FILENAME, "r" ) ) == NULL ) {
    fprintf ( stderr, "fileloop1: Unable to open %s!\n", FILENAME );
    exit ( 1 );
    }
 
   if ( ( outptr = fopen ("east.dat","w") ) == NULL ) {
     fputs("Unable to open east.dat",stderr);
     fclose(outptr) ;
}
 
    while ( fgets( buffer, sizeof buffer, fp ) != NULL ) {
      fputs( buffer, stdout );
    }
 
    for(i=1; i<=10; i=i+2)
     {          
          fgets(buffer, 81, fp);
          fprintf(outptr, "%d: %s", i, buffer);
     }  
 
    for(i=0; i<=10; i=i+2)
     {          
          fgets(buffer, 81, fp);
          fprintf(outptr2, "%d: %s", i, buffer);
     }  
   fclose(fp);
   fclose(outptr);
   flclose(outptr2);

The output of both file1.dat and file2.dat are empty, except the line numbers. Why doesn'it prints the lines ?