read text file and store in array in c programming

Question

I want read text file and store in array then show.

This is my code:

  int i = 0, line = 5;
  char ch[100];

  FILE *myfile;
    myfile = fopen("test.txt","r");
    if (myfile== NULL)
    {
    printf("can not open file \n");
    return 1;
    }

    while(line--){
    fscanf(myfile,"%s",&ch[i]);
    i++;
    printf("\n%s", &ch[i]);
    }

    fclose(myfile);

    return 0;
}

This is my text:

test 123562

856

59986

But result:

est

2356

56

9986

What is wrong? :(

Answer 1

ch[i] is holding a single character. Statement fscanf(myfile,"%s",&ch[i]); will scan string to ch[i] which can hold only one character. There is no place for '\\0' which leads your program to undefined behavior . Change

 
 
 
  
  fscanf(myfile,"%s",&ch[i]);
 
  

to

 
 
 
  
  fscanf(myfile,"%s",ch);
 
  

---

Previous answer was wrong. Behavior of program is well defined but you are scanning the file in a wrong manner. Your program will work as expected if you place i++; after printf statement.

 while(line--){ fscanf(myfile,"%s",&ch[i]); printf("\\n%s", &ch[i]); i++; } 

The reason is that &ch[i] is a pointer to the i ^th element of the array and string will be stored in array starting at position i . For the input given, this will work because the given array is large enough to hold the string.

You can do this as:

 while(line--){ fscanf(myfile,"%s",ch); printf("\\n%s", ch); i++; } 

but it will overwrite the array ch each time a string is scanned to it. Better to use a two dimensional array to store strings and read file with fgets .

Answer 2

You're not going to be able to fit five lines in the single char ch[100] array; that's just an array of 100 characters.

You can make it an array of arrays, ie char ln[5][100] which will give you room for five lines of 100 characters each.

Then you of course need to index into that array in the loop, ie:

for(int i = 0; i < 5; ++i)
{
  if(fgets(ln[i], sizeof ln[i], myfile) == NULL)
  {
    fprintf(stderr, "Read error on line %d\n", i);
    exit(1);
  }
}

This uses fgets() which is much better suited at reading in whole lines; fscanf() will stop at whitespace with %s which is seldom what you want.

Answer 3

There is no need to use the ampersand in the scanf while getting the string. Make that into like this.

fscanf(myfile,"%s",&ch[i]);

to

fscanf(myfile,"%s",ch);

&ch[i] It will get the character for i th position in that array. If you want to get like that you can use the %c instead of %s . And change this one to.

printf("\n%s", ch);

While printing the string when you use the ampersand(&) that will access the address of that variable.

Answer 4

3. The program developed must be able to read the input files containing matrix A and matrix B using fopen function a. Matrix A and B of different size may be stored in different input file (if required).
4. Scan and assign matrix A and B as array using fscanf function and for loop
5. Perform matrix operations a. Add matrix A and B b. Subtract matrix A and B c. Multiply matrix A and B
6. Use conditional statement if or switch for switching between 3, 4 and 5 elements matrix.
7. Print all input matrices and results obtained in a new file called output.dat using fprintf function.
8. The output.dat file must have a header with the following information: a. Student name b. Student matric number c. Class section d. Lecturer name e. Project title
9. Below the header, the output file must contain matrix A and B and the results from matrix operation. Use matrix A and B as given below: