C: Fill array only with the size of scanfed string - c

Question

After i put a name in the terminal and it is shorter, then 20 chars, it wants inputs until i have filled all the 20 positions in the array.
I know it is because of the for cycle i have there, but I don't know how else to fill that end of the array with nothing("").
In the array there is for example this "Helloworld\n123\n123"
Thank you for help in advance.
#define NAME 20
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
main(void) {
char name[NAME] = {""};
malloc(sizeof(name[NAME]));
printf("Choose your name: ");
for (int i = 0; i < NAME; i++) {
scanf("%c", &name[i]);
}
//Welcome and the name
printf("Welcome: ");
for (int i = 0; i < NAME; i++) {
printf("%c", name[i]);
}
return 0;
}

Answer 1

You need to stop reading at a newline (+should also check return codes).
A loop like:
size_t i=0;
for (; i < sizeof(name)-1; i++) {
if (1==(scanf("%c",&name[i]))){ if (name[i]=='\n') break; }
else if (feof(stdin)) break; //end of file?
else return perror("getchar"),1; //report error
}
name[i]='\0';
will achieve that (can also use getchar/getc/fgetc instead of scanf)
or you can use fgets:
if(NULL==fgets(name,sizeof(name),stdin)) return perror("fgets"),1;
//erase a possibly included newline at the end
//(won't be there if you pressed Ctrl+D twice rather than
//Enter to submit your input or if you're at the end of
//a stdin redirected from a file)
size_t len = strlen(name);
if(name[len-1]=='\n') name[len-1]='\0';
Whole program with both versions (in the if(0){...}else{...}) :
#define NAME 20
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>
int main(void) {
char name[NAME] = {""};
//malloc(sizeof(name[NAME])); //a useless memory leak; don't do this!
printf("Choose your name: ");
if(0){
if(NULL==fgets(name,sizeof(name),stdin)) return perror("fgets"),1;
size_t len = strlen(name);
if(name[len-1]=='\n') name[len-1]='\0';
}else{
size_t i=0;
for (; i < sizeof(name)-1; i++) {
if (1==(scanf("%c",&name[i]))){ if (name[i]=='\n') break; }
else if (feof(stdin)) break; //end of file?
else return perror("getchar"),1;
}
name[i]='\0';
}
//Welcome and the name
printf("Welcome: ");
for (int i = 0; i < NAME; i++) {
printf("%c", name[i]);
}
return 0;
}

Answer 2

If you have to use scanf and %c format:
char *readLineUsingCharAndScanf(char *buff, size_t size, FILE *fi)
{
char ch;
char *wrk = buff;
while(size-- && fscanf(fi, "%c", &ch) == 1 && ch != '\n' ) *wrk++ = ch;
*wrk = 0;
return buff;
}
void dumpString(const char *restrict str, size_t size)
{
while(*str && size--)
{
printf("%03d [0x%02x] - %s\n", *str, *str, (*str >= 32 & *str <= 127) ? (char[]){'\'', *str, '\'', 0} : "not printable");
str++;
}
}
int main(void)
{
char name[20];
dumpString(readLineUsingCharAndScanf(name, 19, stdin), 20);
}
https://godbolt.org/z/vWvP68TbW

Answer 3

scanf() is not the best tool for your purpose. Here is a simple and safe solution:
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#define NAME 20
int main(void) {
char name[NAME];
int c;
size_t i;
printf("Enter your name: ");
i = 0;
while ((c = getchar()) != EOF && c != '\n') {
if (i < sizeof(name) - 1)
name[i++] = c;
}
name[i] = '\0';
//Welcome and the name
printf("Welcome: %s\n", name);
return 0;
}
If you must use scanf(), use this:
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#define NAME 20
int main(void) {
char name[NAME];
char c;
size_t i;
printf("Enter your name: ");
i = 0;
while (scanf("%c", &c) == 1 && c != '\n') {
if (i < sizeof(name) - 1)
name[i++] = c;
}
name[i] = '\0';
//Welcome and the name
printf("Welcome: %s\n", name);
return 0;
}

Answer 4

Thank you everyone for answering. Unfortunately the first two answers are too complicated for me yet. And the third one was not working properly.
But I found the simplest answer. :) Many thanks
#include <stdio.h>
int main(void)
{
char name[20];
printf("Choose your name: ");
scanf("%[^\n]*c",name);
printf("My name is %s",name);
}

Answer 5

For your needs I would use scanf with the string conversion specifier %s. In this case, the input name would be read and stored character by character in the buffer until the whitespace would be read. Here is the code.
#define NAME 20
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
char name[NAME] = {""};
malloc(sizeof(name[NAME]));
printf("Choose your name: ");
scanf("%s", &name);
printf("%s", &name);
return 0;
}