CODEWITHSUNDEEP
cwindows
iYehuda
iYehuda

Reputation: 35

input redirection on CMD

Well, I am learning programming in C, and I got an assignment to get 3 characters from an input text file into 3 variables and then print their ASCII values.
I wrote this code:

#include <stdio.h>
int main()
{
  char a,b,c;
  printf("Insert 3 characters:\n");
  a=getch();
  b=getch();
  c=getch();
  printf("%d, %d, %d",(int)a,(int)b,(int)c);
}

I opened a text file (input.txt) and wrote there: "abc".
I managed to compile the code with the MinGW compiler, and on the CMD window that I opened in the folder of the .exe file, I wrote: "Task.exe <input.txt".
The program ran normally. I mean, it waited for me to input 3 characters.

What have I done wrong in my work?
help me please :)

Upvotes: 0

Views: 308

Answers (1)

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

You are asked to read from an input text file.

Why don't you use fopen to open a file handle, and fgetc to read from it?

You could perhaps use fscanf. Don't forget to use the resulting count.

And of course, you should call fclose. Using perror is useful to handle error cases.

So start your code with something that checks that your program has an argument, then fopen it:

int main(int argc, char**argv) {
 if (argc<2) { fprintf(stderr, "missing program argument\n");
               exit(EXIT_FAILURE); };
 FILE* fil = fopen(argv[1], "r");
 if (!fil) { perror(argv[1]); exit(EXIT_FAILURE); };

Then run Task.exe input.txt in your console (no redirection needed!).

You should take the habit of reading the documentation of every function you are using, of testing failure cases, of compiling with all warnings & debug info (gcc -Wall -Wextra -std=c99 -g), and of using the debugger (gdb).

Upvotes: 1

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