How to use toupper library function in C? - c

Question

I need to print the initials of a name, like tyler jae woodbury would print TJW, but I can't seem to print the uppercase initials.
This is my code:
#include <stdio.h>
#include <cs50.h>
#include <ctype.h>
#include <string.h>
string get_initials(string name, char initials[]);
int main(void)
{
// User input
string name = get_string("Name: ");
// Gets the users initials
char initials[10];
get_initials(name, initials);
printf("%s\n", initials);
}
string get_initials(string name, char initials[])
{
int counter = 0;
for (int i = 0, n = strlen(name); i < n; i++)
{
if (name[i] == ' ')
{
initials[counter] = name[i+1];
counter++;
}
else if (i == 0)
{
initials[counter] = name[i];
counter++;
}
}
return initials;
}
I know that usually toupper() is used for chars, and the print statement declares a string, but I don't know what to do.

Answer 1

The function is incorrect.
For starters in general a string can contain adjacent spaces between words or have trailing adjacent spaces.
Secondly the function does not build a string because it does not append the terminating zero character '\0' to the destination array.
Also the call of strlen is inefficient and redundant.
To convert a symbol to upper case use standard function toupper declared in the header <ctype.h>
Also the function declaration is confusing
string get_initials(string name, char initials[]);
Either use
string get_initials(string name, string initials);
or it will be better to write
char * get_initials( const char *name, char *initials);
The function can be defined the following way as shown in the demonstration program below.
#include <stdio.h>
#include <string.h>
#include <ctype.h>
char * get_initials( const char *name, char *initials )
{
const char *blank = " \t";
char *p = initials;
while ( name += strspn( name, blank ), *name )
{
*p++ = toupper( ( unsigned char )*name );
name += strcspn( name, blank );
}
*p = '\0';
return initials;
}
int main( void )
{
char name[] = " tyler jae woodbury ";
char initials[10];
puts( get_initials( name, initials ) );
}
The program output is
TJW