Hello to you all ,

I am having a little trouble in C , working with Files.
for some reason , it doesnt copy to output file the first letter and jumps
over 3 digits of the last number in the file .

whats wrong , i cant find it .

yotam

P.S - source and Input.txt included

> void main
main returns int

> char user_choice;
> while (user_choice!='z')
This variable is uninitialised at the point you first use it.

> university univ;
This isn't initialised either.
Which is very important when you get to make_file(), since you do
- dereference an uninitialised pointer
- try and realloc an uninitialised pointer

> if (un->ptr==NULL) un->ptr=(student*)realloc(un->ptr,(count+1)*sizeof(student));
The test serves no purpose, since at best it only extends the array once.

In main(), you need this to start off with a NULL pointer university univ = { 0 }; And this function needs to be something like

int make_file(FILE *in,university *un) {
  char buff[BUFSIZ];
  int  count=0;

  while ( fgets( buff, sizeof buff, in ) != NULL ) {
    student s;
    if ( sscanf( buff, "%s %ld %f %ld",
                 s.name, &s.id, &s.avg, &s.hw_submit ) == 4 ) {
      /* success decode, extend array and copy the info */
      void *temp = realloc( un->ptr, (count+1)*sizeof(student) );
      if ( temp != NULL ) {
        un->ptr = temp;          /* update array */
        un->ptr[count] = s;      /* copy data */
        count++;                 /* one more stored */
      } else {
        /* no more room, return with what we have */
        return count;
      }
    } else {
      /* that line didn't make sense, report it */
      fprintf( stderr, "Bad line %s", buff );
    }
  }
  return count;
}

> void main
main returns int

> char user_choice;
> while (user_choice!='z')
This variable is uninitialised at the point you first use it.

> university univ;
This isn't initialised either.
Which is very important when you get to make_file(), since you do
- dereference an uninitialised pointer
- try and realloc an uninitialised pointer

> if (un->ptr==NULL) un->ptr=(student*)realloc(un->ptr,(count+1)*sizeof(student));
The test serves no purpose, since at best it only extends the array once.

In main(), you need this to start off with a NULL pointer university univ = { 0 }; And this function needs to be something like

int make_file(FILE *in,university *un) {
  char buff[BUFSIZ];
  int  count=0;

  while ( fgets( buff, sizeof buff, in ) != NULL ) {
    student s;
    if ( sscanf( buff, "%s %ld %f %ld",
                 s.name, &s.id, &s.avg, &s.hw_submit ) == 4 ) {
      /* success decode, extend array and copy the info */
      void *temp = realloc( un->ptr, (count+1)*sizeof(student) );
      if ( temp != NULL ) {
        un->ptr = temp;          /* update array */
        un->ptr[count] = s;      /* copy data */
        count++;                 /* one more stored */
      } else {
        /* no more room, return with what we have */
        return count;
      }
    } else {
      /* that line didn't make sense, report it */
      fprintf( stderr, "Bad line %s", buff );
    }
  }
  return count;
}

I did so , however , only the first name was fixed .... how bizzare.
1. what does "buff" stands for , after all it has no Value.
2.BUFSIZ shoulde be defined or resized each reading from source file?
3.how can get rid of the double menu display?
4.is there a way to write to target file so it wont skip chars?

thanx salem

1. what does "buff" stands for , after all it has no Value.
buff is short for buffer.

2.BUFSIZ shoulde be defined or resized each reading from source file?
No, it is a fixed constant declared in stdio.h (for an ANSI-C compiler anyway).
You are using an ANSI-C compiler and not some ancient fossil like TurboC.

3.how can get rid of the double menu display?
Don't use getchar(), scanf(), getc() to read a single character.
Use fgets() to read a line from stdin, then read what you need from the buffer.
It's just like my use of fgets() in the previous post.

4.is there a way to write to target file so it wont skip chars?
I've no idea - post the problem code.