Using scanf with the %s format specifier will only read a single word. If you want to read an entire line consisting of several words (e.g. "Linus Torvalds\n"), then I suggest that you use fgets instead. However, beware of this problem regarding mixing fgets and scanf. Also, see this question on how to remove the newline character from the fgets input. I suggest that you don't use scanf at all for user input, but instead always use fgets.
The condition if("Linus Torvalds\n") does not make sense, as that condition will always be true. If you want to compare the content of name with "Linus Torvalds\n", then you need to use the strcmp function.
Also, the line
if (strcmp("n", yesno)){
is wrong, because the function strcmp requires both of its arguments to be a pointer that each point to a string, i.e. to a sequence of characters terminated by a null character. However, yesno is not a pointer. &yesno would also be wrong, because such a pointer would only point to a single character, not to a sequence of characters terminated by a null character.
The function strcmp will return zero if the two strings match, and non-zero if they don't. Therefore, you probably want to compare the return value of strcmp with zero.
I suggest that you rewrite your program like this:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void get_line_from_user( const char prompt[], char buffer[], int buffer_size );
int main( void )
{
char input[200];
get_line_from_user(
"Hello adventurer, are you here to learn Linux? (y/n) ",
input, sizeof input
);
if ( strcmp( input, "y" ) == 0 )
{
get_line_from_user(
"Great! What is your name? ",
input, sizeof input
);
if ( strcmp( input, "Linus Torvalds" ) == 0 )
{
printf( "Achievement complete: In God We Trust\n" );
printf( "Nice to meet you! My name is Richard Stallman.\n" );
}
else
{
printf( "Nice to meet you! My name is Linus Torvalds.\n" );
}
}
else if ( strcmp( input, "n" ) == 0 )
{
printf( "Ok! Bye!" );
}
else
{
printf( "That's not an answer.\n" );
}
}
//This function will read exactly one line of input from the
//user. It will remove the newline character, if it exists. If
//the line is too long to fit in the buffer, then the function
//will automatically reprompt the user for input. On failure,
//the function will never return, but will print an error
//message and call "exit" instead.
void get_line_from_user( const char prompt[], char buffer[], int buffer_size )
{
for (;;) //infinite loop, equivalent to while(1)
{
char *p;
//prompt user for input
fputs( prompt, stdout );
//attempt to read one line of input
if ( fgets( buffer, buffer_size, stdin ) == NULL )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
//attempt to find newline character
p = strchr( buffer, '\n' );
//make sure that entire line was read in (i.e. that
//the buffer was not too small to store the entire line)
if ( p == NULL )
{
int c;
//a missing newline character is ok if the next
//character is a newline character or if we have
//reached end-of-file (for example if the input is
//being piped from a file or if the user enters
//end-of-file in the terminal itself)
if ( (c=getchar()) != '\n' && !feof(stdin) )
{
if ( c == EOF )
{
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
printf( "Input was too long to fit in buffer!\n" );
//discard remainder of line
do
{
c = getchar();
if ( c == EOF )
{
//this error message will be printed if either
//a stream error or an unexpected end-of-file
//is encountered
printf( "Error reading from input!\n" );
exit( EXIT_FAILURE );
}
} while ( c != '\n' );
//reprompt user for input by restarting loop
continue;
}
}
else
{
//remove newline character by overwriting it with
//null character
*p = '\0';
}
//input was ok, so break out of loop
break;
}
}
This program has the following behavior:
Hello adventurer, are you here to learn Linux? (y/n) y
Great! What is your name? Jimmy
Nice to meet you! My name is Linus Torvalds.
Hello adventurer, are you here to learn Linux? (y/n) y
Great! What is your name? Linus Torvalds
Achievement complete: In God We Trust
Nice to meet you! My name is Richard Stallman.
Hello adventurer, are you here to learn Linux? (y/n) n
Ok! Bye!
Hello adventurer, are you here to learn Linux? (y/n) sdfsdgf
That's not an answer.
