reading and saving known number of lines of unknown lengths of strings - c

Question

I want to receive the number of lines of input from the user then read and save the lines of unknown lengths in an array.
I know that the way I am saving the lines is wrong but I don't know how to correct it.
int nos; // number of strings
scanf_s("%d", &nos);
char** strs = malloc(nos * sizeof(char*)); // array of strings
for (int i = 0; i < nos; i++) // receiving strings
{
scanf_s("%s", (strs+i));
}

Answer 1

You're close, but you're forgetting to allocate memory for the string. If you're working with POSIX-compliant systems (i.e. pretty much everything except Windows) then use the %ms scanf() format specifier to allocate the buffer for the string as you're reading it (note that this stops after whitespace):
scanf("%ms", &strs[i]);
For Windows, implement a gets()-like function:
#include <stdlib.h>
#include <stdio.h>
int msgets(char **str)
{
int ch = 0;
size_t len = 0;
while(ch != '\n')
{
len++;
*str = realloc(*str, len);
ch = getchar();
(*str)[len-1] = ch;
}
(*str)[--len] = 0;
return len;
}
Here's how to use it in replacement of the scanf() line:
msgets(&strs[i]);
Other than that, your code looks fine.
Here's an almost complete example with my code included:
#include <stdlib.h>
#include <stdio.h>
int msgets(char **str)
{
int ch = 0;
size_t len = 0;
while(ch != '\n')
{
len++;
*str = realloc(*str, len);
ch = getchar();
(*str)[len-1] = ch;
}
(*str)[--len] = 0;
return len;
}
int main(void)
{
int nos; // number of strings
scanf("%d ", &nos);
char** strs = malloc(nos * sizeof(char*)); // array of strings
for (int i = 0; i < nos; i++) // receiving strings
{
msgets(&strs[i]);
}
/* Do something with strs[] here */
return 0;
}

Answer 2

if you read carefully this answerHow can I read an input string of unknown length? , and modify your code it should be something like this.
I also add a print for loop to see the results of this code
#include <stdio.h>
#include <stdlib.h>
char *inputString(FILE* fp, size_t size){
char *str=NULL;
int ch;
size_t len = 0;
str = realloc(str, sizeof(char)*size);
if(!str){
printf("[DEBUG]\n");
return str;
}
while(EOF!=(ch=fgetc(fp)) && ch != '\n'){
str[len++]=ch;
if(len==size){
str = realloc(str, sizeof(char)*(size+=16));
if(!str)return str;
}
}
str[len++]='\0';
return realloc(str, sizeof(char)*len);
}
void empty_stdin (void) /* simple helper-function to empty stdin */
{
char c;
while ((c = getchar()) != '\n' && c != EOF);
return;
}
int main(void){
int nos,i; /*number of strings*/
scanf("%d", &nos);
empty_stdin();
char ** strs = malloc(nos * sizeof(char*)); /*array of strings*/
for (i = 0; i < nos; i++) {/*receiving strings*/
*(strs+i) = inputString(stdin,1);
}
for(i=0;i<nos;i++){
printf("%s\n",*(strs+i));
}
return 0;
}
input:
3
123456789
foo
hello world
output:
123456789
foo
hello world