representation of hexadecimal numbers in c

Question

I have the following numbers which I read from a file.
These numbers are read as strings. I need to represent them as hexadecimal numbers.
How do I do that?

"I need to represent them as hexadecimal numbers." - please clarify. — Karoly Horvath, Dec 24 '13 at 17:15
Do you mean you want to convert the strings in hex notation to integers? — 0xbe5077ed, Dec 24 '13 at 17:16
@0xbe5077ed i want to convert these string I read(which have hex format) to hex numbers. — user3133067, Dec 24 '13 at 17:21
@KarolyHorvath The compiler should see this strings which have hex format as hex numbers. — user3133067, Dec 24 '13 at 17:22
Please check Stackoverflow for questions similar to yours before posting. In this case there are more then one. — alk, Dec 24 '13 at 17:22

score 3 · Answer 1 · 2013-12-26T10:26:27.313

3

Since you want to read these numbers from a file, fscanf is helpful for this:

/* note, if you're using more than 8 digits, 
    this would have to be unsigned long long and instead of %lx you would need %llx */
unsigned long h;
if (fscanf(f, "%lx", &h) == 1)
    do whatever with h
else
    error, check errno

You can use this check in a loop while (fscanf(f, "%x\n", &h) == 1); to read until the last number.

edited Dec 26 '13 at 10:26

answered Dec 24 '13 at 17:20

1

Better use `unsigned h;`. – alk Dec 24 '13 at 17:21
Yeah, thanks! 3more to go – Dec 24 '13 at 17:25
1

`"\n"` in `"%x\n"` serves no purpose. Suggest eliminating it. `"%x"` consumes leading whitespace already. `fscanf(f, "%x\n", &h)` will return 1 with or without a `\n` following the number. – chux - Reinstate Monica Dec 24 '13 at 22:17
"if you're using more than **4** digits, ...." as `unsigned` is only at least 0 to 65535. Better to use `unsigned long` here. – chux - Reinstate Monica Dec 24 '13 at 22:20
@chux `unsigned` defaults to `unsigned long int` anyway. Now it is `unsigned long` to make more sense. – Dec 26 '13 at 00:32
2

@user9000 Suggest `"%lx\n"` to go with `unsigned long`. BTW: "unsigned defaults to unsigned long int" is _not_ so. `unsigned`, same as `unsigned int`, does not default to anything other than it has at least the range of `unsigned short` and no more range than `unsigned long`. By the C spec §5.2.4.2.1, the minimum `unsigned` range is the same as minimum `unsigned short` range. – chux - Reinstate Monica Dec 26 '13 at 01:01

score 3 · Answer 2 · answered Dec 24 '13 at 17:20

3

If you have already read them into a character buffer, you could use strtol to convert from base 16 (pass 16 as the 3rd parameter).

Alternatively, if you are reading them from the file, you could fscanf with the %x conversion specifier.

answered Dec 24 '13 at 17:20

Mark Wilkins

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representation of hexadecimal numbers in c

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