Thread: Best Way to Read Input from User (error for whitespace)

  1. #1
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    Join Date
    Sep 2020
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    6

    Best Way to Read Input from User (error for whitespace)

    I'm writing a program that takes in single words from a user. The goal is for the program to take in ONLY a single word (i.e. if there is space in the user's input, it will trigger an error).

    I've read a lot of things about the pros and cons of the different input methods (scanf, gets, fgets, etc), and think I want to avoid gets.

    Currently I'm working with:

    Code:
        gettimeofday(&start, NULL);
        for (int i = 0; i < n; ++i){
            do{
                printf("Word number %d: %s\n>", i+1, arr[i]);
                scanf("%10s", word);
                scanf("%*[^\n]"); scanf("%*c");
          
                if(strcmp(arr[i], word) != 0){
                    printf("Incorrect.\n");
                    correct = 0;
                }
    
                else{
                    correct = 1;
                }
            } while (correct == 0);
        }
        gettimeofday(&stop, NULL);
    
    
    



    This works, but counts for example "word word" as just "word" (by scanf stopping at whitespace).

    Does anyone have any recommendations or advice about how to go about accomplishing what I'm trying to do?

    Or suggestions on the scanf/fgets debate?

  2. #2
    Registered User
    Join Date
    Dec 2017
    Posts
    1,136
    think I want to avoid gets
    gets doesn't even exist in the current language spec.

    You should definitely use fgets since your input is basically "line based" where you only want one word on the line.

    One possibility:
    Code:
    #include <stdio.h>
    
    
    int main() {
        char line[1000], word[100], extra[2];
     
        while (1) {
            printf("Enter one word: ");
            fgets(line, sizeof line, stdin);
            extra[0] = '\0';
            sscanf(line, "%99s%1s", word, extra);
            if (extra[0] == '\0') break;
            printf("I said ONE WORD!!! Try again...\n");
        }
     
        printf("You entered: %s\n", word);
     
        return 0;
    }
    Another possibility:
    Code:
    #include <stdio.h>
    #include <string.h>
     
    int main() {
        char line[1000], word[100];
     
        while (1) {
            printf("Enter one word: ");
            fgets(line, sizeof line, stdin);
            int pos = 0;
            sscanf(line, "%99s%n", word, &pos);
            if (line[strspn(line + pos, " \t\n") + pos] == '\0') break;
            printf("I said ONE WORD!!! Try again...\n");
        }
     
        printf("You entered: %s\n", word);
     
        return 0;
    }
    The best argument against democracy is a five minute conversation with the average voter. - Churchill

  3. #3
    Registered User
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    Sep 2020
    Posts
    6
    Awesome, I will give that a try. Thank you.

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