Using fgets() right after getchar()

Question

void
read_stdin(trace_t* trace, state_t state, action_t** action_list) {
    // initial stage
    int c;
    while ((c = getchar())!= EOF && c!='#') {
        if (my_isalpha(c)==LOWERCASE) {
            state[c-ASCII_CODE_LOWER_A] = '1';
        }
    }
    printf("%s\n", state);

    char str[2];
    fgets(str, 2, stdin);
    printf("%s", str);
}

If '#' is the last character I enter in the getchar() loop, fgets() records the newline character from when I press enter and skips to the print statement immediately (which prints the '\n')

I could fix this by adding an additional fgets()(which has to have a string that is longer than 1 char passed to it for some reason?) but is there a more elegant way of solving this?

Antti Haapala · Accepted Answer · 2020-10-26 08:41:11Z

2

Well, you can use scanf("%*[\n]"); to ignore any number of consecutive newline. Or scanf("%*1[\n]"); for eating only one newline. If any other character is the first one, it is not consumed.

Another option would be to use low-level operations getchar and ungetc:

int eat_stdin_newline(void) {
    int ch = getchar();
    if (ch != EOF && ch != '\n') {
        // if it wasn't EOF or newline, push it back...
        ungetc(ch, stdin); // must succeed
    }
    return ch;
}

Then you can call this function wherever you want:

eat_stdin_newline();

answered Oct 26, 2020 at 8:41

Antti Haapala

135k23 gold badges297 silver badges349 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Using fgets() right after getchar()

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related