Reading STDIN and outputting it from a function

Hi all, I'm working on an app that will read stdin and simply pass it to a function that ouputs it. I have this so far:

Code:

---

#include <stdio.h>

void code_here(char inputData[]);


int main(){
  char arr[512];
  fread(arr, 1, 512, stdin);
  code_here(arr);
  return 0;
}


void code_here(char inputData[]) {
  // Use this function to output your solution
  puts(inputData);
}

---

Things appear to work but I wanted to sanity check here that things look ok. Thanks for any guidance.

FYI: puts requires a zero terminated array; your code does *not* ensure that this is true.

Edit: Read about the return value of fread.

Tim S.

Quote:

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Originally Posted by stahta01

FYI: puts requires a zero terminated array; your code does *not* ensure that this is true.

Edit: Read about the return value of fread.

Tim S.

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Thanks Tim. I read about the size value that fread returns. In my case I'm hitting an EOF I believe. When I examine the output, there is an odd character at the end.
My first guess would be to strcat() a `\0` to the end of the buffer. If that doesn't work, I'm probably taking the wrong approach.

Quote:

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Originally Posted by dmarr

My first guess would be to strcat() a `\0` to the end of the buffer.

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You cannot use strcat because strcat itself expects a null terminated string to concatenate to.

Rather, as stahta01 implied, fread returns the number of items read, and since you're specifying each item is one byte, it returns the number of bytes read. Use that to directly write a null character (but then you should pass 511, or more flexibly sizeof(arr) - 1, as the third argument to fread since you need to reserve at least one element for the null character).

@laserlight Thank you for your help. I am having a hard time understanding how to "use that to directly write a null character". I used the 511 value in the fread call, but I still see the bad character come back in the result.

It would be

Code:

---

  char arr[512];
  n = fread(arr, 1, sizeof(arr)-1, stdin);
  if ( n > 0 ) {
    arr[n] = '\0';
    code_here(arr);
  }

---

Code:

---

#include "stdio.h"
#include "string.h"

char* input(char* buffer, size_t size)
{
 fgets(buffer, size, stdin);
 char* newline = strstr(buffer, "\n");
 if(newline)
  *newline = 0;
 return buffer;
}

int empty(char* text)
{
 return text == NULL || *text == 0;
}

int main(void)
{
 char data[1024];
 for(;;)
 {
  printf("Input (empty line to exit): ");
  if(empty(input(data, sizeof(data))))
  break;
  puts(data);
 }
}

---

Quote:

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Originally Posted by Salem

It would be

Code:

---

  char arr[512];
  n = fread(arr, 1, sizeof(arr)-1, stdin);
  if ( n > 0 ) {
    arr[n] = '\0';
    code_here(arr);
  }

---

---

Shouldn't we write '\0' even if n==0, giving us an empty string corresponding to 0 bytes read?

> Shouldn't we write '\0' even if n==0, giving us an empty string corresponding to 0 bytes read?
Only if code_here(arr) actually did anything useful with a zero length string, other than saying "oh, it's zero length, nothing to do".

The n == 0 case indicates either an error (use ferror() to find out) or end of file (use feof() to find out).