Member Avatar for BHKK

Hi, I got a problem in reading and write on file.
I have to create an virtual agenda, therefore I enter a name and a number for N persons.
After entering the infos if the file doesn't exist, the program create it and save the infos, if the file exist the program will overwrite all the lines.

But when i write on screen the information from a fprintf the lines are messed up.

I load the infos form the file with this:

    fp=fopen("agenda.txt","r");
            if(fp)
            {
                rewind(fp);
                while(!feof(fp))
                {
                    fscanf(fp,"%s %s",inome,inum);
                    if(ii==NULL)
                    {
                        head=malloc(sizeof(agenda));
                        if(!head)
                        {
                            printf("Memory Problems");
                            exit(1);
                        }
                        head->prev=NULL;
                        head->next=NULL;
                        strcpy(head->nome,inome);
                        strcpy(head->num,inum);
                        ii=head;
                        fflush(stdin);
                    }

And i save the info from the memory to the file with this

void save()
{
    fp=fopen("agenda.txt","w");
    ptr ii=head;
    rewind(fp);
    while(ii)
    {
        fprintf(fp,"%s %s",ii->nome,ii->num);
        ii=ii->next;
    }
    fclose(fp);
    return;
}

This is what happens after that the program writes on screen the infos from the file

  • 4 Contributors
  • 4 Replies
  • 186 Views
  • 1 Day Discussion Span
  • Latest Post Latest Post by Ancient Dragon

Dani AI

Generated

Brief diagnosis and concrete fixes for 's thread (builds on comments from and others):

The visible symptom (records running together) is almost certainly a missing line terminator when saving plus fragile parsing and list construction when loading. correctly called out the newline issue; the posted use of fflush(stdin) is undefined behavior, and while(!feof(fp)) with fscanf("%s %s",...) is fragile (it fails for names with spaces and misdetects EOF). Also the loader only allocates the head node and never appends a new node for each record, which explains corrupted/incomplete list state that follows.

Safe, practical changes (examples follow):

  • Write one logical record per line and include a newline. Use snprintf + fputs or fprintf that ends with \n.
  • Read full lines with fgets() and parse the line (tab or another delimiter is safer than whitespace tokenization). Check the parse function return value before using data.
  • Initialize head/tail/iterator pointers to NULL before loading and allocate a new node for every parsed line; link next/prev correctly and update the tail.

Example patterns (illustrative; adapt field sizes and types):

/* append record safely */
FILE *fp = fopen("agenda.txt", "a");
char buf[256];
snprintf(buf, sizeof buf, "%s\t%s\n", name_buf, num_buf);
fputs(buf, fp);
fclose(fp);
/* read line-by-line and parse */
char line[256];
while (fgets(line, sizeof line, fp)) {
    char name[128], num[64];
    if (sscanf(line, "%127[^\t]\t%63s", name, num) != 2) continue;
    /* allocate node, copy safely, link into list */
}

Checklist / cautions:

  • Check return values for fopen, fgets, malloc, sscanf.
  • Avoid fflush(stdin); use fgets for console input or consume leftover chars with a getchar loop.
  • Use bounded string functions (snprintf, strncpy/strlcpy) to prevent overruns.
  • Decide whether files should be overwritten ("w") or appended ("a") and open accordingly.

These changes address the line-termination, input-parsing, and linked-list allocation issues noted in the replies from and .

Recommended Answers

All 4 Replies

Member Avatar for Ancient Dragon

fprintf(fp,"%s %s",ii->nome,ii->num);

The problem is that you have to put '\n' at the end. And your program won't work at all if you put a space in the name that you enter, such as "John Smith" or something like that.
fprintf(fp,"%s %s\n",ii->nome,ii->num);

Edited by Ancient Dragon
Member Avatar for firdousahmad

ur program is incomplete plz upload ur full program

Member Avatar for Rouf mir

I feel that it should work fine but some problem is in memory allocation

Edited by Rouf mir
Member Avatar for Ancient Dragon

I feel that it should work fine but some problem is in memory allocation

Contridction! if there is a prblem then it is not working find :)

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