I have encounter an error when running this code. There will be a "program stop working" windows once it reaches the loop to scan for user input for the names ("scanf_s(%s", &nameptr[i]); ).
Any help or advice will be greatly appreciated!
#include <stdio.h>
#include <string.h>
#define SIZE 10
int findTarget(char *target, char nameptr[SIZE][80], int size);
int main()
{
char nameptr[SIZE][80];
char t[40];
int i, result, size;
printf("Enter no. of names: ");
scanf_s("%d", &size);
printf("Enter %d names: ", size);
for (i = 0; i < size; i++)
scanf_s("%s", &nameptr[i]);
printf("Enter target name: ");
scanf_s("\n");
gets(t);
result = findTarget(t, nameptr, size);
printf("findTarget(): %d\n", result);
return 0;
}
int findTarget(char *target, char nameptr[SIZE][80], int size)
{
int i;
for (i = 0; i<size; i++) {
if (strcmp(nameptr[i], target) == 0)
return i;
}
return -1;
}
This:
scanf_s("%s", &nameptr[i]);
should be
scanf_s("%s", nameptr[i], sizeof(nameptr[i]));
/* Or better */
scanf_s("%79s", nameptr[i], sizeof(nameptr[i]));
or
scanf_s("%s", nameptr[i], _countof(nameptr[i]));
/* Or better */
scanf_s("%79s", nameptr[i], _countof(nameptr[i]));
because the %s in scanf_s expects a third argument denoting the maximum size of the string argument used. More information on this can be found at the msdn documentation of scanf_s
Related
New picture from an external compiler.. the exit code is ok?
enter image description here
This is the full code. I'm having a trouble program blows away after printing the wanted output to the screen. I guess it's a problem with the way I allocated memory for the array of structs, and the .name field of each struct in a for loop.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>
#define MAX_NAME_LEN 50
typedef struct stud
{
char *name;
int marks[4];
float avg;
}student;
student* Create_Class(int);
void Avg_Mark(student*);
void Print_One(student*);
void printExcellent(student*);
void main()
{
int size, i;
student *arr, *newArr;
printf("\nEnter the number of students: ");
scanf_s("%d", &size);
newArr = Create_Class(&size);
for (i = 0; i < size; i++)
{
printExcellent(newArr+i);
}
for (i=0;i<size;i++) free(newArr[i].name);
free(newArr);
_getch();
}
student* Create_Class(int size)
{
student *p;
char str[MAX_NAME_LEN];
int i, j;
p = (student*)calloc(size , sizeof(student));
if (!p)
{
printf("Memory allocation failure.");
exit(1);
}
for (i = 0; i < size; i++)
{
printf("Enter your name: ");
rewind(stdin);
gets(str);
p[i].name = (char*)calloc(strlen(str)+1,sizeof(char));
if (!(p[i].name))
{
printf("Memory allocation error!");
exit(1);
}
strcpy_s(p[i].name,50,str);
printf("Enter your marks: ");
for (j = 0; j < 4; j++)
{
scanf_s("%d", &p[i].marks[j]);
}
Avg_Mark(p + i);
}
return p;
}
void Avg_Mark(student* s)
{
int i, sum=0;
for (i = 0; i < 4; i++)
sum += s->marks[i];
s->avg = (float)sum / 4;
}
void Print_One(student* s)
{
printf("The average of %s is %.1f\n", s->name, s->avg);
}
void printExcellent(student* s)
{
if ((s->avg) > 85)
Print_One(s);
}
Gonna point out everything fishy I see for you:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>
#define MAX_NAME_LEN 50
typedef struct stud
{
char *name;
int marks[4];
float avg;
}student;
student* Create_Class(int);
void Avg_Mark(student*);
void Print_One(student*);
void printExcellent(student*);
void main()
{
int size, i;
student *arr, *newArr;
printf("\nEnter the number of students: ");
scanf_s("%d", &size);
// This is wrong. Remove the &...
newArr = Create_Class(&size);
for (i = 0; i < size; i++)
{
printExcellent(newArr+i);
}
for (i=0;i<size;i++) free(newArr[i].name);
free(newArr);
_getch();
}
student* Create_Class(int size)
{
student *p;
char str[MAX_NAME_LEN];
int i, j;
// Consider checking size for a sane value.
// Ok, allocate an array of students.
p = (student*)calloc(size , sizeof(student));
if (!p)
{
printf("Memory allocation failure.");
exit(1);
}
for (i = 0; i < size; i++)
{
printf("Enter your name: ");
// These 2 lines scare the heck out of me. I'd really do this differently.
// gets is the devil and the see:
// https://stackoverflow.com/questions/20052657/reversing-stdin-in-c
// for why this may not work well.
rewind(stdin);
gets(str);
// What if str is not a terminated string? Then 1 char of 0? Guess this is ok. Hope it doesn't overflow on the copy below though (consider fixed max size and not using a temporary)
p[i].name = (char*)calloc(strlen(str)+1,sizeof(char));
if (!(p[i].name))
{
printf("Memory allocation error!");
exit(1);
}
// Do a fast copy of up to 50 chars. I'd really want to verify this output to be sure it works.
strcpy_s(p[i].name,50,str);
printf("Enter your marks: ");
for (j = 0; j < 4; j++)
{
// Hope this inputs the way you want.
scanf_s("%d", &p[i].marks[j]);
}
// This should work, but I prefer more explicit pointers.
Avg_Mark(p + i);
}
return p;
}
void Avg_Mark(student* s)
{
// What if s is Null?
int i, sum=0;
// 4 is a magic number. Make this a constant.
for (i = 0; i < 4; i++)
sum += s->marks[i];
// This won't be as accurate as you want. Consider an integer solution.
s->avg = (float)sum / 4;
}
void Print_One(student* s)
{
// What if s is Null? What about s->name?
printf("The average of %s is %.1f\n", s->name, s->avg);
}
void printExcellent(student* s)
{
// What if s is Null?
if ((s->avg) > 85)
Print_One(s);
}
Note: While going through this code, I did not see any "red flags" except for the & on the size and perhaps the gets/rewind calls. I'd still add null asserts to your functions and also walk through it with a debugger to be sure that everything is as you expect. Honestly, there is enough going on here that I'd prefer the debugger help to my quick trace of the code while I was writing comments.
Update
If I change all your scanf_s to scanf() calls, replace your gets() / rewind() calls to a simple scanf("%s", str) call, and change your funky strcpy_s() function to a simpler strcpy() or strncpy() call, your program does not seem to crash for me. My money is that the strcpy_s() call is corrupting RAM while doing its "fast" copy.
I want to have unknown amount of inputs in a single line. For example, user can input:
"ans: 1 2 3 4 5"
and scanf() will store these five numbers to an array. The problem is that the program don't know how many input will there be.
#include <stdio.h>
int main()
{
int i;
int input[4];
scanf("ans: " for(i = 0, i < 3,i++){scanf(" %d", &input[i]);};
return 0;
}
Sorry I'am totally new to coding, what will be the proper way to write this? Or is this impossible?
Thanks :)
Use fgets() and sscanf() with "%n"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char input[100];
int arr[10];
//fgets(input, sizeof input, stdin);
strcpy(input, "1 2 42 56 -3 0 2018\n"); // fgets
char *pi = input;
int tmp, pp, i = 0;
while (sscanf(pi, "%d%n", &tmp, &pp) == 1) {
if (i == 10) { fprintf(stderr, "array too small\n"); exit(EXIT_FAILURE); }
pi += pp;
arr[i++] = tmp;
}
printf("got this ==>");
for (int k = 0; k < i; k++) printf(" %d", arr[k]);
puts("");
}
You asked this question way round.
You can achieve what you expect by putting scanf inside of a loop.Even you can ask user to give how many inputs he want to enter.
#include <stdio.h>
int main()
{
int i;
int input[4];
printf("Enter the number of inputs you want to give : ");
scanf("%d", &n);
for(i = 0; i < n;i++)
{
printf("Enter the input number %d : ",i);
scanf("%d", &input[i]);
}
return 0;
}
I'm trying to create a program with a loop that prompts the user to enter data in the array elements. And when the user no longer can enter data, print to screen the data entered in a last in, first out order.
And this is my attempt...
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
struct Name_Age
{
char Name[10];
int Age;
};
void printMe(struct Name_Age info)
{
printf("Name: %s\n", info.Name);
printf("Age: %d\n", info.Age);
}
int main()
{
int size = 0, i = 0, j = 0;
struct Name_Age * array_ptr = (struct Name_Age*)malloc((size + 1)* sizeof(struct Name_Age));
struct Name_Age myInfo = *array_ptr;
printf("Enter size of array: ");
scanf("%d\n", size);
for (i = 0; i < size; ++i)
{
printf("Enter Name: \n");
scanf("%s\n", myInfo.Name);
printf("Enter Age: \n");
scanf("%d\n", myInfo.Age);
}
printMe(myInfo);
return 0;
};
First, scanf("%d", &size) replace scanf("%d\n", size), put &size instead of size as argument(You need an address), and put the malloc things after this line of code, because you need an exact size value before malloc. Same thing with all the scanf stuffs.
As you want to print out all your input names and ages in order, I changed your code like this:
#include <stdio.h>
#include <stdlib.h>
struct Name_Age
{
char Name[10];
int Age;
};
void printMe(struct Name_Age *infoList, int size)
{
int i;
for (i = size-1; i >= 0; --i)
{
printf("Name: %s\n", infoList[i].Name);
printf("Age: %d\n", infoList[i].Age);
printf("\n");
}
}
int main()
{
int size, i;
printf("Enter size of array: ");
scanf("%d", &size);
struct Name_Age * array_ptr = (struct Name_Age*)malloc(size* sizeof(struct Name_Age));
for (i = 0; i < size; ++i)
{
printf("Enter Name: \n");
scanf("%s", array_ptr[i].Name);
printf("Enter Age: \n");
scanf("%d", &array_ptr[i].Age);
}
printMe(array_ptr, size);
return 0;
}
Try to test and compare with your code, questions are welcome.
You can use fgets to read strings and cast the string to digits with atoi. The storage is not complete, but with my changes you can read to structs and specify the size of the loop (TODO: Save a list of structs so that you actually can print a list of structs that you have specified.)
#include <stdio.h>
#include <stdlib.h>
struct Name_Age {
char Name[10];
int Age;
};
void printMe(struct Name_Age info) {
printf("Name: %s\n", info.Name);
printf("Age: %d\n", info.Age);
}
int main() {
int size = 0, i = 0, j = 0;
struct Name_Age *array_ptr = malloc((size + 1) * sizeof(struct Name_Age));
struct Name_Age myInfo = *array_ptr;
printf("Enter size of array: ");
char tmp[10];
fgets(tmp, 10,stdin);
size = atoi(tmp);
for (i = 0; i < size; ++i) {
printf("Enter Name: ");
fgets(myInfo.Name, 10,stdin);
printf("Enter Age: ");
fgets(tmp, 10,stdin);
myInfo.Age = atoi(tmp);
}
printMe(myInfo);
return 0;
};
Test
$ ./a.out
Enter size of array: 2
Enter Name: Superman
Enter Age: 25
Enter Name: Batman
Enter Age: 27
Name: Batman
Age: 27
See also this question about fgets fgets how to read int
Obviously using fgets() is a much better approach, but making the fewest amount of changes as possible to your code and still achieving your result is the following:
#include <stdio.h>
#include <stdlib.h>
struct Name_Age
{
char Name[10];
int Age;
};
void printMe(struct Name_Age *info);
int main(void)
{
int size, i;
struct Name_Age *array_ptr;
printf("Enter size of array: ");
scanf("%d", &size);
array_ptr = malloc(size * sizeof *array_ptr);
for (i = 0; i < size; ++i)
{
printf("Enter Name: ");
scanf(" %s", array_ptr[i].Name);
printf("Enter Age: ");
scanf("%d", &array_ptr[i].Age);
printf("\n");
}
for (i = 0; i < size; ++i)
printMe(&array_ptr[i]);
return 0;
}
void printMe(struct Name_Age *info)
{
printf("Name: %s\n", info->Name);
printf("Age: %d\n", info->Age);
}
Note that passing the struct by pointer to the function should be faster, note that you don't need the myInfo struct; you can just directly modify the elements of the array. Note the space before %s in the scanf() line, this is to discard any whitespace (including \n), this is done automatically for %d so it is only necessary for your strings (technically not the first iteration of the loop, but it doesn't fail if no whitespace is found). If you have any questions about why I made the changes I did, please feel free to comment on this answer!
example of fix
//struct Name_Age myInfo = *array_ptr;//Not necessary
printf("Enter size of array: ");
scanf("%d", &size);//remove `\n`, add `&`
//To ensure after the size has been determined
struct Name_Age * array_ptr = (struct Name_Age*)malloc(size * sizeof(struct Name_Age));//Cast is not necessary in C
for (i = 0; i < size; ++i)
{
printf("Enter Name: \n");
scanf("%s", array_ptr[i].Name);//remove `\n`
printf("Enter Age: \n");
scanf("%d", &array_ptr[i].Age);//need `&`
}
for (i = 0; i < size; ++i)
printMe(array_ptr[i]);
I have char array to store string values. I wanted to store the value of a string variable into the char array.
char Password[30];
char User[2];
int i;
for(i=0; i<5; i++) {
printf("Enter Password");
scanf("%s", Password);
strcpy(User[i],Password,30);
}
I wanted to input the values for the array and it should throw a buffer overflow but I couldn't do it. How can I do it?
This should work for you:
#include <stdio.h>
#include <string.h>
int main() {
char Password[30];
char User[5][30];
int i;
for(i = 0; i < 5; i++) {
printf("Enter Password");
scanf("%s", Password);
strcpy(User[i],Password);
}
for(i = 0; i < 5; i++)
printf("Password %d: %s\n", i+1, User[i]);
return 0;
}
The second for loop is to show the output and that every thing is stored right!
I am having a few issues with my code. First: when I try to compile, I get error: too few arguments to function 'strcmp'. I have looked all over and made multiple changes and am still unable to get it to work. Second: when my code does compile (if I remove the strcmp part), it will not complete the count functions correctly. Can anyone please assist? Thank you!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int count(char array[], int size);
int stringLen(char array[]);
int convert(char ch);
int value, n;
int main()
{
//char * str;
//char s;
char a[100];
char b[100];
char c[100];
int charCount = stringLen(a);
int lCount = count(a, charCount);
printf("Enter your string: \n");
scanf("%s \n", a);
printf("Enter your string: \n");
scanf("%s \n", b);
printf("Enter your string: \n");
scanf("%s \n", c);
printf("The count is %d, length is %d\n", lCount, charCount);
int i;
for(i = 0; i < charCount; i++)
{
char c = a[i];
printf("Char %s = %d \n", &c, value);
}
n = strcmp(char string1[], char string2[], char string3[]);
printf("The first string in the alphabet is: %d \n", n);
return 0;
}
int stringLen(char array[])
{
char count;
int index;
while(array[index] !=0)
{
count++;
index++;
}
return count;
}
int count(char array[], int size)
{
int count;
int i;
for(i = 0; i < size; i++)
{
if(array[i] == 'a')
{
count ++;
}
else if(array[i] == 'A')
{
count ++;
}
}
return count;
}
This is not right way to use strcmp.
n = strcmp(char string1[], char string2[], char string3[]);
strcmp is used for compararison of string. See doc
int result = strcmp (string1,string2)
If strings are same, function will return 0.