So I'm finally reading through K&R, and I learned something within the first few pages, that there is a backspace escape character, \b
.
So I go to test it out, and there is some very odd behavior:
#include <stdio.h>
main ()
{
printf("hello worl\b\bd\n");
}
The output is
hello wodl
Can anyone explain this?
Your result will vary depending on what kind of terminal or console program you're on, but yes, on most \b
is a nondestructive backspace. It moves the cursor backward, but doesn't erase what's there.
So for the hello worl
part, the code outputs
hello worl ^
...(where ^
shows where the cursor is) Then it outputs two \b
characters which moves the cursor backward two places without erasing (on your terminal):
hello worl ^
Note the cursor is now on the r
. Then it outputs d
, which overwrites the r
and gives us:
hello wodl ^
Finally, it outputs \n
, which is a non-destructive newline (again, on most terminals, including apparently yours), so the l
is left unchanged and the cursor is moved to the beginning of the next line.
.......... ^ <= pointer to "print head"
/* part1 */
printf("hello worl");
hello worl ^ <= pointer to "print head"
/* part2 */
printf("\b");
hello worl ^ <= pointer to "print head"
/* part3 */
printf("\b");
hello worl ^ <= pointer to "print head"
/* part4 */
printf("d\n");
hello wodl ^ <= pointer to "print head" on the next line
If you want a destructive backspace, you'll need something like
"\b \b"
i.e. a backspace, a space, and another backspace.
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