C - User input getting skipped?

Question

I want a menu from which you choose some action.

Problem is that when we choose one, and press the \"return\" key, the user input command which should have been the

Answer 1

scanf() leaves a newline which is consumed by the subsequent call to gets().

Use getchar(); right after scanf() or use a loop to read and discard chars:

int c;
while((c= getchar()) != '\n' && c != EOF); 

I know you have commented about gets() being bad. But you shouldn't even attempt to use it even if it's a toy program. It's been removed from the latest C standard (C11) completely and shouldn't be used even if you are programming for C89 (due to its buffer overflow vulnerabilities). Use fgets() which does almost the same except possibly leaves a trailing newline.

If this is your complete code, then you would also need a prototype or at least a declaration for do_this(). Implicit int rule has also been removed from C standard. So add,

int do_this();

at the top of your source file.