isdigit

[bazzano]

Hey guys just a question related to the function isdigit() how come if i wish to check if its not a digit it wont work work. Even if i type in an integer it still says that bad input is entered i only want it to print the error if they type in any other character except for integers.


eg

if((!isdigit(h))
{
     printf("bad input: integers only!\n");
     return 0;
}

[hk_mp5kpdw]

Show some more code, like where you declare h and where you ask for a get the characters from the user.

And this...

if((!isdigit(h))
{
     printf("bad input: integers only!\n");
     return 0;
}

... has one to many parenthesis.

[Salem]

Probably because you're trying to use isdigit() on the converted result, not a character in the input string.

char buff[] = "123";
int h = strtol( buff, NULL, 0 );

if ( isdigit( buff[0] ) )
Would be OK to call before strtol().
But so would calling isdigit( buff[1] ) and isdigit( buff[2] ) - in other words, a LOOP.

if ( isdigit(h) )
Isn't going to work unless by some small chance you typed in a number between 48 and 56.

[dwks]

Even if i type in an integer it still says that bad input is entered i only want it to print the error if they type in any other character except for integers.

How are you parsing the numbers from the input? Most functions that do this (scanf(), strtol(), etc) have a return value or an error state of some sort that you can check for. Here's a scanf() example.

int x, c;

printf("Enter a number: ");
while(scanf("%d", &x) != 1) {
    while((c = getchar()) != '\n' && c != EOF);  /* flush the input buffer */
    printf("Invalid number. Try again: ");
}