'Control reaches end of non-void function' in C

I am trying to read the user's input. When I compile the program I get the message, 'control reaches end of non-void function [-Wreturn-type] }'.

char *read_line(char *buf, size_t sz) {
    while(fgets(buf, sz, stdin)) {
        fputs(buf, stdout);
    }
}

int main(int argc, char** argv) {
    char *buf;

    read_line(buf, 1024);
}

I want the program to take the user's input, press enter, and have their input printed back out to them. I gotta do it using the methods I have used (it's part of some homework).

I don't fully know what is going on under the hood of C, so it is just causes some many problems like this :).

For starters the function has undefined behavior because it uses an unitialized pointer.

And the function shall have a return statement if its return type is not void.

It seems you mean the following

#include <stdio.h>

void read_line( char *buf, size_t sz ) 
{
    while( fgets(buf, sz, stdin) && buf[0] != '\n' ) 
    {
        fputs(buf, stdout);
    }
}

int main( void ) 
{
    enum { N = 1024 };
    char buf[N];

    read_line( buf, N );
}

Or something like the following

#include <stdio.h>

char * read_line( char *buf, size_t sz ) 
{
    if  ( fgets(buf, sz, stdin) && buf[0] != '\n' ) 
    {
        return buf;
    }
    else
    {
        return NULL;
    }
}

int main( void ) 
{
    enum { N = 1024 };
    char buf[N];

    char *p = read_line( buf, N );\

    if ( p != NULL ) fputs( p, stdout );
}