getch and ungetch ??

[kalar]

I can't understand how ungetch works. I read an explanation on kernighan and ritchie book but i can't understand.Can anyone give me a simple example??
Also, should i include any header file expect stdio?
Thanks

[JosAH]

I can't understand how ungetch works. I read an explanation on kernighan and ritchie book but i can't understand.Can anyone give me a simple example??
Also, should i include any header file expect stdio?
Thanks

If I remember well that name of the function is ungetc() (without the 'h'). It simply
'pushes back' the character you supply as an argument to that function.
Basically:

#include <stdio.h>
...
char a;
a= getc(stdin);
printf("a: %c\n", a);
ungetc(a);
a= getc(stdin);
printf("a again: %c\n", a);
 

There are no other files you have to include. Read this.

kind regards,

Jos

[Banfa]

As Jos says the standard library function is ungetc, however checking my trusty copy of Kernighan and Richie they also define an ungetch which (along with getch) is just a function they write to wrap the standard libraries getchar.

I will assume that you want an explaination for ungetch as define by K&R, the function simply writes the data back to a buffer allocated specifically for the purpose of holding this ungot data. Then the getch function checks to see if the unget buffer is empty and if it is not it returns a character from the unget buffer and decrements the amount of data in it. Otherwise if the buffer is empty it just calls the standard library getchar.

[kalar]

Yes, I mean ungetch. Thank you.