Print pointer character as hexadecimal

Question

#include <stdio.h>

int main(){
    char *c="";
    printf("Input: ");
    scanf_s("%c", c);
    printf("%x", *c);
}

I want to input a few characters, and then output the entire string as a hexadecimal value. How do I do this?

score 2 · Accepted Answer · answered May 11 '12 at 01:02

2

You need a buffer, not a string constant, to read into. Also, never use any of the *scanf functions, and never use any of the *_s functions either.

The correct way to write your program is something like this:

int
main(void)
{
  char line[80];
  char *p;

  fputs("Input: ", stdout);
  fgets(line, sizeof line, stdin);

  for (p = line; *p; p++)
    printf("%02x", *p);

  putchar('\n');
  return 0;
}

... but I'm not sure exactly what you mean by "output the entire string as a hexadecimal value" so this may not be quite what you want.

answered May 11 '12 at 01:02

zwol

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Scanning a single character at a time might not be the best way to do it, but it's not invalid either. – Mark Ransom May 11 '12 at 01:03
this worked, but is there anyway to do this all at once? also why is scanf bad practice? – Painguy May 11 '12 at 01:20
Sorry, do what all at once? I don't understand what you're asking. – zwol May 11 '12 at 04:38
Regarding `scanf`, see here: http://stackoverflow.com/questions/9134208/input-by-using-gets-function/9134440#9134440 – zwol May 11 '12 at 04:39

score 1 · Answer 2 · answered May 11 '12 at 00:59

1

Your entire code is wrong. It should look something like this:

printf("Input: ");

char c = fgetc(stdin);
printf("%X", c);

answered May 11 '12 at 00:59

Richard J. Ross III

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Your code is just as wrong as the original, in that it stops after a single character. – Mark Ransom May 11 '12 at 01:04

score 0 · Answer 3 · answered May 11 '12 at 00:59

0

You need a loop to read multiple characters and output each of them. You probably want to change the format to %02x to make sure each character outputs 2 digits.

answered May 11 '12 at 00:59

Mark Ransom

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score 0 · Answer 4 · answered May 11 '12 at 01:26

#include <stdio.h>

int main(void)
{
    unsigned int i = 0;              /* Use unsigned to avoid sign extension */
    while ((i = getchar()) != EOF)   /* Process everything until EOF         */
    {
        printf("%02X ", i);
    }

    printf("\n");

    return 0;
}

Print pointer character as hexadecimal

4 Answers4