C Program Help in Upper Casing First Letter of Input - c

Question

I am a beginner coder and writing a code that
asks for the user's name
check if the length is >15, if it is, it will ask the user to input a shorter name when they restart the program
if the length is valid, upper case the first letter of the entered name
display something like "Hi name"
However, The program keeps exiting no matter what I enter. Here is what I did :
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <conio.h>
int main(void)
{
char str_name[15];
printf("Please enter your first name to begin: ");
scanf_s("%14s", str_name, _countof(str_name));
getchar();
if (strlen(str_name) > 15)
{
printf("The entered name is too long, please restart the program and try again.");
getchar();
exit(0);
}
else
{
str_name[0] = toupper(str_name[0]);
printf("Hi %s.\n", str_name);
getchar();
}
return 0;
}

Answer 1

You can simply use fgets() to read an input buffer.
char *fgets(char *str, int n, FILE *stream) reads a line from the specified stream and stores it in a buffer pointed to by str. It stops when either n-1 characters are read, the newline character is read, or the EOF is reached.
Some things to note about fgets():
Returns NULL on error.
Appends \n character at the end of buffer. Can replaced with \0 instead.
Buffer must be pointer to an array of characters. Either allocated on the stack or the heap.
Reads from stdin or FILE objects.
Here is some example code which shows this:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define NAMESTRLEN 16
int main(void) {
char str_name[NAMESTRLEN] = {'\0'};
size_t slen;
printf("Please enter your first name to begin: ");
if (fgets(str_name, NAMESTRLEN, stdin) == NULL) {
fprintf( stderr, "Error from fgets()\n");
return 1;
}
slen = strlen(str_name);
if (slen > 0 && str_name[slen-1] == '\n') {
str_name[slen-1] = '\0';
} else {
fprintf( stderr, "Too many characters\n");
return 1;
}
if (str_name[0] == '\0') {
fprintf( stderr, "No name entered\n");
return 1;
}
str_name[0] = toupper((unsigned char)str_name[0]);
printf("Hi %s.\n", str_name);
return 0;
}

Answer 2

There are several issues in your code:
The buffer size is too short: scanf() will not read more than 14 bytes into str_name, so it is not possible to test if the user entered a name longer than 15 characters.
toupper() should not be given a char argument because it is only defined for values of type unsigned char and the special value EOF. Cast the char as unsigned char.
your attempt at pausing before the terminal window closes fails on windows for long names because the extra characters entered by the user are still pending after the scanf_s(). getchar() reads one and returns immediately, and the program exits and the terminal window closes. Open the terminal window and run the program manually so it does not close automatically. With this approach, you can remove the getchar() and make the program more portable.
Here is a corrected version:
#include <ctype.h>
#include <stdio.h>
int main(void) {
char str_name[17];
printf("Please enter your first name to begin: ");
if (scanf_s("%16s", str_name, sizeof(str_name))) {
printf("Premature end of file.\n");
return 1;
}
if (strlen(str_name) > 15) {
printf("The entered name is too long, please restart the program and try again.");
return 1;
}
str_name[0] = toupper((unsigned char)str_name[0]);
printf("Hi %s\n", str_name);
return 0;
}

Answer 3

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
int main(void)
{
char str_name[16] = {0};
size_t len = 0;
int ch;
printf("Please enter your first name to begin: ");
while ((EOF != (ch = fgetc(stdin))) && (ch != '\n') && (len<sizeof(str_name)))
{
if (isalpha(ch))
{
str_name[len++] = ch;
}
}
if (len==sizeof(str_name))
{
fprintf(stderr, "Name too long\n");
}
else
{
str_name[len] = '\0';
printf ("Hi %c%s.\n", toupper(str_name[0]), &str_name[1]);
}
return 0;
}
As you can see I changed the input grabbing function. To check the input str len you should read byte per byte, not a whole string: fgetc do it. Using scanf with a format specifier like %14s it will return you always a trimmed string and you are not able to warn user about a too long Name.
Another point is to check that inserted chars are letters and not other kind of chars: isalpha do the job.
Moreover a c-string is composed by chars plus a null terminator ('\0', 0x00 ), so: a 15 chars string wants a 16 bytes array.
Lastly the code you wrote to mahe the first letter uppercase is completely wrong: you are passing to print a 1 char array and not a c string. My solution is one of many.

Answer 4

The problem is:
char Name[1]; // Declare a single element array.
Name[0] = toupper(str_name[0]); // Set it to the upper-case first letter.
// Try and print the nul-terminated string in Name - but there is no
// trailing zero (and the rest of the name is missing).
printf("Hi %s.\n", Name);
What you need is:
str_name[0] = toupper(str_name[0]);
printf("Hi %s.\n", str_name);
There is another problem that str_name[0] is a char value, and char may be signed. If you are using Windows-1252 for example, then Ä is 196, or as a signed char, -60. toupper takes an int, which must be positive¹. When -60 as a signed char is converted to int, you will get -60, and an out of range error. You need to write this as:
str_name[0] = toupper((unsigned char)str_name[0]);
printf("Hi %s.\n", str_name);
(Sorry.)
¹ Chrqlie points out the requirement is actually that the argument must be one of the values of unsigned char (which are - by definition - non-negative) or EOF (which is negative)"