I can not input the names into the char array using scanf

Question

I can not use scanf to enter a name in stdnames array. when compiled it had no error , but as soon as i enter a name and then press enter to write the other name it gives an error and shuts the program. How should I go about it ?

int main(int argc, char* argv[])
{
  float marks[50];
  /*char *stdnames[100]={"Arvind Thillainathan","Robert Lang"};*/
 //I want to stores names like the above one
  char *stdnames[100];
  int totalNames = 0;
  int i = 0, w=0,h=0;

 printf("How many names do you want to enter ??\n");
 scanf("%d",&totalNames);
 assert(totalNames != 0);

 for(int count = 0; count < totalNames; count++)
 {
     printf("Enter name of student\n");
     scanf("%s",stdnames[count]);
 //From here the problem starts
 }
 getres(marks,totalNames);

 for(i = 0; i < totalNames; i++) 
      {
        int v = 1;
        printf("\n");
        printf("IELTS Marks of %s\n\n",stdnames[i]);
        for(h = w; h < w+5; h++)
           {
            if(v==1)
            {
                printf("Listening : %0.1f\n", marks[h]);
            }
            else if(v==2)
            {
                printf("Reading   : %0.1f\n", marks[h]);    
            }
            else if(v==3)
            {
                printf("Writing   : %0.1f\n", marks[h]);    
            }
            else if(v==4)
            {
                printf("Speaking  : %0.1f\n", marks[h]);    
            }
            else
            {
                printf("Overall   : %0.1f\n\n", marks[h]);
            }
            v++;
            //if(h==10)
            //{
            //  break;
            //}
        }
        w+=5;
}
return 0;
}

You're scanfing to an unallocated object stdnames[count]. Perhaps try allocating some memory there first with say malloc. — Antti Haapala
– Antti Haapala, Commented May 11, 2016 at 19:16
You might also run into trouble with float marks[50]; when you have char *stdnames[100]; although the loop that inputs marks is a bit obfuscated. — Weather Vane
– Weather Vane, Commented May 11, 2016 at 19:24
There is no "char array". You mean that array of pointers to char? — too honest for this site
– too honest for this site, Commented May 11, 2016 at 19:29
@arvind-dexter-thillainathan : consider including the definition for getres(marks,totalNames) in the code. — sjsam
– sjsam, Commented May 11, 2016 at 19:48

sjsam · Accepted Answer · 2016-05-12 01:29:27Z

1

By

char *stdnames[100];

you got an array of (pointers to char).

The NEXT BIG QUESTION is

Who will allocate memory for each of these pointers?

A small answer would be - You have to do it yourself like below :

stdnames[count]=malloc(100*sizeof(char)); // You may replace 100 with desired size

or

stdnames[count]=malloc(100); // sizeof(char) is almost always 1

You need to put this line before the scanf statement.

Note: Don't forget to free the allocated memory once these variables become irrelevant. Do it like :

free(stdnames[count]);

edited May 12, 2016 at 1:29

answered May 11, 2016 at 19:18

sjsam

22k6 gold badges62 silver badges114 bronze badges

Sign up to request clarification or add additional context in comments.

18 Comments

too honest for this site Over a year ago

That boldfaces hurts in the eyes. And sizeof(char) is useless, as it will never yield something other than 1.

sjsam Over a year ago

@Olaf : Hurted mine too. changed :D

too honest for this site Over a year ago

Thanks (still it is a bit too loud for me, but I can stand that - have to read Word-Docs and PPT anyway). There are other issues with the contents.

too honest for this site Over a year ago

Ehm, that would be correct (and independent of the type), but actually I wonder why not just remove that term?

Arvind Dexter Thillainathan Over a year ago

@sjsam thanks man, it worked perfectly. I just started C. What's the exact purpose of malloc ?

|

Collectives™ on Stack Overflow

I can not input the names into the char array using scanf

1 Answer 1

18 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

18 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related