read char from console | 易学教程

问题

I write console application which performs several scanf for int And after it ,I performs getchar :

int x,y;
char c;
printf("x:\n");
scanf("%d",&x);
printf("y:\n");
scanf("%d",&y);
c = getchar();

as a result of this I get c = '\n',despite the input is:

1
2
a

How this problem can be solved?

回答1:

This is because scanf leaves the newline you type in the input stream. Try

do
    c = getchar();
while (isspace(c));

instead of

c = getchar();

回答2:

You can use the fflush function to clear anything left in buffer as a consquence of previous comand line inputs:

fflush(stdin);

回答3:

A way to clean up anyspace before your desired char and just ignore the remaining chars is

do {
    c = getchar();
} while (isspace(c));
while (getchar() != '\n');

回答4:

For a start the scanf should read scanf("%d\n", &x); or y. That should do the trick.

man scanf

回答5:

Call fflush(stdin); after scanf to discard any unnecessary chars (like \r \n) from input buffer that were left by scanf.

Edit: As guys in comments mentioned fflush solution could have portability issue, so here is my second proposal. Do not use scanf at all and do this work using combination of fgets and sscanf. This is much safer and simpler approach, because allow handling wrong input situations.

int x,y;
char c;
char buffer[80];

printf("x:\n");
if (NULL == fgets(buffer, 80, stdin) || 1 != sscanf(buffer, "%d", &x))
{
    printf("wrong input");
}
printf("y:\n");
if (NULL == fgets(buffer, 80, stdin) || 1 != sscanf(buffer, "%d", &y))
{
    printf("wrong input");
}
c = getchar();

来源：https://stackoverflow.com/questions/8853154/read-char-from-console

标签

scanf

getchar