Cannot scan data using fscanf into array in c

Question

I am writing a program that can mark the students' result. However I have problem to scan to input file data into array before I analyze them. This is my input data structure:

BECDCBAADEBACBAEDDBE

2019000  BEAABEBCCDDEECXBEBXC

2019001  ABXBBDAXAEAAEAABECED

2019002  ABBCXCBBCBAXCCBEAEAD

The first line is the correct answer. Below included the student number and their answer. Currently I just want to save the data inside array. This is what I tried:

#include <stdio.h>
#include <string.h>

// Function Prototype
void ReadFile(char* correct_ans, int* number, char student_ans[100][20]);

int main(void)
{
    char correct_ans[20], student_ans[100][20];
    int student_number[100];

    FILE *fp1;
    fp1 = fopen("answer.txt", "r");
    int temp;
    char temp_answer[20];
    
    fscanf(fp1, "%s\n", correct_ans);

    
    for(int i = 0; i < 100; i++)
    {
        fscanf(fp1, "%d %s\n", &student_number[i], temp_answer);

        strcpy(*(student_ans + i), temp_answer);
    }
    
    printf("%s\n", correct_ans);
    for(int i = 0; i < 100; i++)
    {
        printf("%d %s\n", student_number[i], student_ans[i]);
    }
    
    return 0;
}

When I run the code:

2019000 BEAABEBCCDDEECXBEBXCABXBBDAXAEAAEAABECEDABBCXCBBCBAXCCBEAEADACDEDCEDXECDABBCDACCCADCCEAAXDEEBACDBBXXAXCBEACCDACCCDBCADBDEAXXXBCDEXEBDAACXCDEXXEBEXBAABXBDBEDXDACAAACAXADXAAAABDDADCXEXDECXCBEEDCDXACDEBCACCECCACAADDXBCCXECDEXCEBBCEABADCAAEXXXECXDCBEEBACEBBEAEEDBBAABBDBDCBXEBABBDXAEDXCDBDEDDCXECDACBCDCECADBEDEXABXADXCDCDAACBEBECEAXADCDAEDAECECAAEBXEXBBACABCCEAXADDEEDECCXAEXBXEXBEAAEXABDXXXEAEBXEAACEXXDDABDADACAXXCDXXACAADXEDXDXBDACECBEEAECAEXABDBAABEBXBBCEXBCEACBCAXXBXBXEXACCCCAACXXXXCXEDECEBDCDDCEDEXDCXAECXEBXBDDBCXEDXDAXCCABXEBAEXEEXBCABXAXABECAECBXDXBDXCCDXDABEBXXBBDEAXECCCAEDDCXXABXCABXXCAEAXAEEECDEACXDXECDCDCBXAADCECBXDXDBDABAXABACEXXCEDBDEBDCDXBDBAEEEEEBCBCACXCBXBEXDDCDBXCADABXCACACBEBCEXBBCACDEDEXXCDXEBBCCXBDXEXBAEDCCCCXCEXABABDXEDADECEEEXABDBABBAABBBCBBADBEXDXECEXCXDADAXEEBABADECBECXXAAACCAAAXBAACBBXXBBXEXADCBBADXBDACCBDAXBDEBCAXABABBDACCACDABADADBXCADBADADCXCEACBBADAEEXEEEEEXBBBCEEABBXCDDDDEDEXAAEBCDEEXEAEXEECXCEBCBADDXDXEBEDCECDXBAEAAEBBADEEDEDDEXXBCDDAABADADDBAXBXECDDBEXBBDEDCBADEEXEECBDCXCDXACCBBXBDXBEBBCEEXEEXDDADECABEAXEDCEDDDBDXBAXECBECDBEXBCBADDXXBXBEXDCCDBDAECBBCCAEDEEBAXDXXCEAAEDXEBCDXXDXDAADADBEDCXXCBCABABAABAECDECACDDEBCCAACAEBXEXXCEBABXEDCEXBBBCAEXABAEXXBADBACEEBDAAEXDDECCXDCBXBEEAEAXEADACBECEEADAEXXXEXBXAECXEAECCCXADCDCBCDDBCAEBAABDBXXEDAAXCCXXDABCXBXDDCBCECCCEXCXXABEABECEDBXADECCBBCEECEDEBBBBEAAXXCXEXEXCDCCECCAEABXXBDCEAAEADDXXACDXCXBXXCADBAXABXXCDBEBXEBDBEBECBDXCXDDEEDCDAAXABCCEBDABDBXCXEBXAEBXDCXBBCBDDEBDCBBDDCDEEXACDBDXXDBAEEBEBCCCXEAACEBECEEEDEBXAEXECBCBECEDCBEAEXEDDADBCEADEXCECABCCDXAXAXECCEAXEBAEEAAXBEXEXEDCBXBXDBXEBCXEXBACCXXXBXXEADDXXAABECXBEEXXBCXDEXEXDCDACEADEXXCDCBXEDBCBAEADAEBDCCDAXAABXCADCADCBCEEAXBDCXDCACCCDCDXXCBXCDCECXEBAXBXACBBBDBBXCECBAXCXBECAAEDDCCDBCEXEBDAXEXDDCAXXCXEBXXEBCADXBBBBBXDEECXBBBDEEEDACDCEEAADDEEAEDAXACAXDXCEXBACCEEEXBCAEADXBEDEBXDXEEXEBCCABDCCBBDXDACXBXCXDABXDDEADDCDDBBCAAAADAXCDBXXXXACABCADXCEXBXDXEXXEXXCCDDCCEXDXBBBCCBEBADEADCBECXDECEBDECXXDDXDXBCADEEECCXECBBCDAACBCACDCCXXDDCXDAECAEEAXDCEBXBAEXACCBDEBECABEBCDECBDD

This is just the front part of result, seems the answer of all students are accumulated and keep decreasing until the last one:

2019095 
CCBEBADEADCBECXDECEBDECXXDDXDXBCADEEECCXECBBCDAACBCACDCCXXDDCXDAECAEEAXDCEBXBAEXACCBDEBECABEBCDECBDD

2019096 DECXXDDXDXBCADEEECCXECBBCDAACBCACDCCXXDDCXDAECAEEAXDCEBXBAEXACCBDEBECABEBCDECBDD

2019097 ECBBCDAACBCACDCCXXDDCXDAECAEEAXDCEBXBAEXACCBDEBECABEBCDECBDD

2019098 CXDAECAEEAXDCEBXBAEXACCBDEBECABEBCDECBDD

2019099 ACCBDEBECABEBCDECBDD

I am quite new to stackoverflow and not so sure how to edit my question. Sorry to it, but my problems are

The first correct answer cannot print out (means it didnt save to array?)
The answer of students keep accumulating

What I want is that the correct answer should be stored in correct_ans, and the student number is scanned according to the answer. Thx for ur help

You are ignoring the return value at your own risk. You are aware of the return value which is perfect for finding out things in problematic situations, aren't you? As a first step find them out and report them here. — Yunnosch, Feb 11 '22 at 10:07
`char correct_ans[20]` is too small. It is only big enough to store a _string_ of length 19. — chux - Reinstate Monica, Feb 11 '22 at 10:08
Please see [What is the effect of trailing white space in a scanf() format string?](https://stackoverflow.com/questions/19499060/what-is-the-effect-of-trailing-white-space-in-a-scanf-format-string) Remove the `\n` from the `fscanf` format strings. — Weather Vane, Feb 11 '22 at 10:59

alinsoar · Accepted Answer · 2022-02-11T10:29:43.090

The length of the string

CCBEBADEADCBECXDECEBDECXXDDXDXBCADEEECCXECBBCDAACBCACDCCXXDDCXDAECAEEAXDCEBXBAEXACCBDEBECABEBCDECBDD

is larger than sizeof(temp_answer).

From the

    fscanf(fp1, "%d %s\n", 
           &student_number[i],
           temp_answer);

on, the result is undefined.

If you replace the hardcoded constant 20 with a bigger amount, it should work.

Also, there is no need to a temp_answer here, you can read directly in student_ans[i].

Cannot scan data using fscanf into array in c

1 Answers1