copying a string into a structure array

Question

So I have this code below, in my code i load a bunch of movies into an array of structures, Now i know the problem is happening in here (strcpy(parts[x].rating,sp); and what it looks like the strcpy is not working properly, can anyone give me a hint or something useful i can use to solve the problem? I have tried doing it without the strcpy but it doesn't work either !

struct movies
{
char *name;
char *rating;
int time;
float rtwo,rone,rthree; 
};

void displayData(movies *);
 main ()
{
struct movies parts[6];
FILE *fp;
char line[100];

fp=fopen("movies.csv","r");
if (fp == NULL)
{
    printf("Could not locate file");
    exit(0);
}

char *sp;
int x = 0;
    while (fgets(line,100,fp)!=NULL) 
    { 

        sp=strtok(line,",");  
        strcpy(parts[x].name,sp);    


        sp=strtok(NULL,","); 
        strcpy(parts[x].rating,sp);  

        sp=strtok(NULL,","); 
        sscanf(sp,"%d", &parts[x].time);
        sp=strtok(NULL,","); 
        sscanf(sp,"%f", &parts[x].rone);
        sp=strtok(NULL,","); 
        sscanf(sp,"%f", &parts[x].rtwo);
        sp=strtok(NULL,","); 
        sscanf(sp,"%f", &parts[x].rthree); 
        ++x;
    } 
fclose(fp);
displayData(parts);
return 0;
}

void displayData(movies *parts)
{
for (int x=0; x < 6 ; ++x) 
{
    printf("\n Name: %s RATED: %s Time:%d crit: %.1f crit: %.1f crit: 
    %.0f",parts[x].name,parts[x].rating,parts[x]
    .time,parts[x].rone,parts[x].rtwo,pa
    rts[x].rthree); 

    }
}

and yes i did #include <string.h> and all other necessary libraries . — Ali Soujod
– Ali Soujod, Commented Jun 15, 2017 at 22:24
There is no array in your structure! A pointer is not an array! — too honest for this site
– too honest for this site, Commented Jun 15, 2017 at 22:27
@Olaf A structure array is this ( movies parts[6]; ), look at my declaration! — Ali Soujod
– Ali Soujod, Commented Jun 16, 2017 at 0:36
@AliSoujod: That's an array of structures, not a "structure array"! Details are important in programming - gt used to them. As a sidenote: you cannot copy a string to an array of structures: wrong types! You can copy a C string (which is only a convention, not a distinct type) to an array of char, though. It is not relevant where the array is contained. — too honest for this site
– too honest for this site, Commented Jun 16, 2017 at 8:24

Stephan Lechner · Accepted Answer · 2017-06-15 23:23:09Z

1

The main issue is that you do not reserve target memory for the string you want to copy. Note that a struct movies-object provides a data member name, which allows to store a pointer to a sequence of character values, but not the character values themselfes. Hence, strcpy(parts[x].name,sp) accesses the (uninitialized) pointer parts[0].name (which is already UB by itself); the pointer points probably to "somewhere", and then you copy a string to "somewhere".

So you'd have to use malloc first, before calling strcpy; or you could use strdup, which does malloc and strcpy in one call:

    sp=strtok(line,",");  
    parts[x].name = malloc(strlen(sp)+1);
    strcpy(parts[x].name,sp);

or:

    sp=strtok(line,",");  
    parts[x].name = strdup(sp);

Further, you should check if strtok actually returned something valid, e.g. like:

    if ((sp=strtok(line,",")) == NULL)
       continue;
    parts[x].name = strdup(sp);

answered Jun 15, 2017 at 23:23

Stephan Lechner

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1 Comment

Ali Soujod Over a year ago

Thank you, it WORKED ! I looked at not one or two, but multiple examples from stack-overflow but couldn't find a solution! now i understand that I have to allocate the memory before copying the string!

FrenchToast · Accepted Answer · 2017-06-15 22:26:46Z

0

Been a while since I played with C, but, don't you need to malloc parts[x].rating before using it? Same thing with parts[x].name and any other char pointer you have.

answered Jun 15, 2017 at 22:26

FrenchToast

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