function crashes when reading in a csv file

Question

I have coded a function to read in a csv file but half way through the parsing the program crashes giving me errors in strcat.The errors are at the third field which is phone.I can't spot the error I have made in this read function.Anyone have an idea where I'm going of track here?

struct contact *readFile( struct contact *ptrList)
{
    struct contact *head, *newContact;
    FILE *fptr;
    char oneLine[CONTACT_MAX];
    char *sn, *fn, *ph, *co;
    head = ptrList;


    //open test.csv to be read
    fptr = fopen("test.csv", "r");

    if( fptr == NULL )
    {
        printf("\nCouldn't open %s...");
        return(ptrList);
    }
    fgets(oneLine, CONTACT_MAX, fptr);

    while( !feof(fptr) )
    {
        fgets(oneLine, CONTACT_MAX, fptr); // process the next line to be tokenized
        if (oneLine[strlen(oneLine) - 1] == '\n')
        {
            oneLine[strlen(oneLine) - 1] = '\0';
        }
        sn = strtok(oneLine, " , ");
        fn = strtok(NULL, " , ");
        ph = strtok(NULL, " , ");
        co = strtok(NULL, " , ");

        if ( head == NULL )
        {
            head = (struct contact *)malloc(sizeof(struct contact));
            ptrList = head;
                strcpy(head->fName,fn);
                strcpy(head->sName,sn);
                strcpy(head->phone,ph);
                strcpy(head->company,co);

            head->prev = NULL;
            head->next = NULL;

        }
        else
        {
            newContact = (struct contact *)malloc(sizeof(struct contact));
            head->next = newContact;
            newContact->prev = head;
            newContact->next = NULL;

            strcpy(newContact->fName, fn);
            strcpy(newContact->sName, sn);
            strcpy(newContact->phone, ph);
            strcpy(newContact->company, co);

            head = newContact;
        } // end of (ptrList == NULL)

    } // end of while( !feof(fptr))
    fclose(fptr);
    return(ptrList);

This is how I defined contact:

struct contact {
                char sName[CONTACT_MAX+1];
                char fName[CONTACT_MAX+1];
                char phone[CONTACT_MAX+1];
                char company[CONTACT_MAX+1];
                struct contact *prev;
                struct contact *next;
                };

You didn't initialise `head` to `NULL` before using it (in the `if`-condition) — Kninnug, Apr 26 '13 at 20:47
I just did that but it still crashing..What else do you think it could be? — user2324059, Apr 26 '13 at 20:53
As @ValeriAtamaniouk asked, how exactly is `struct contact` defined? You may need to allocate the strings in there as well. Also, don't you mean errors in `strcpy` instead of `strcat`? — Kninnug, Apr 26 '13 at 20:57
yes the errors are showing in strcat file that the parsing is failing at the third field when it comes to the letter 'p'. — user2324059, Apr 26 '13 at 20:59
I can think of `strtok` returning `NULL`, and also if `oneLine` is empty string, then you can corrupt stack a bit. — Valeri Atamaniouk, Apr 26 '13 at 21:00
I added the contact struct definition as asked.How would I go about allocating the strings? @Kninnug — user2324059, Apr 26 '13 at 21:01
`printf("\nCouldn't open %s...");` //Argument is not enough, for `%s` — BLUEPIXY, Apr 26 '13 at 21:02
this func has a process that reads the record even though there is no record probably. — BLUEPIXY, Apr 26 '13 at 21:10

Valeri Atamaniouk · Accepted Answer · 2013-04-26T21:20:57.890

1

Here I've tried to summarize:

sn = strtok(oneLine, " , ");
fn = strtok(NULL, " , ");
ph = strtok(NULL, " , ");
co = strtok(NULL, " , ");

You are relying heavily on correct format, which might not be the case.

sn = strtok(oneLine, " , ");
fn = sn ? strtok(NULL, " , ") : NULL;
ph = fn ? strtok(NULL, " , ") : NULL;
co = ph ? strtok(NULL, " , ") : NULL;

if (!co) continue; // bad string

As BLUEPIXY noted:

printf("\nCouldn't open %s...", "test.csv");

Allocations can look simpler in C:

head = malloc(sizeof(*head));

fgets can fail:

if (fgets(oneLine, CONTACT_MAX, fptr) == NULL) break; // error, do something...

And un-initialized head variable (thanks to Kninnug):

struct contact *head = NULL; // otherise it contains garbage

edited Apr 26 '13 at 21:20

answered Apr 26 '13 at 21:07

Valeri Atamaniouk

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Thanks for the input,I tried the above code but I'm still getting a parsing error. – user2324059 Apr 26 '13 at 21:17
@user2324059 You mean it still crashes? – Valeri Atamaniouk Apr 26 '13 at 21:17
@user2324059 I've added `head` initialization. – Valeri Atamaniouk Apr 26 '13 at 21:21
just added the snippet to intialize the head but ts still crashing. – user2324059 Apr 26 '13 at 21:28
@user2324059 do you know where? – Valeri Atamaniouk Apr 26 '13 at 21:32

function crashes when reading in a csv file

1 Answers1