How to Print Only the Hex Values from Hexdump Without the Line Numbers or the Ascii Table

Commandline hexdump with ASCII output?

hexdump -C does what you want.

# hexdump -C /etc/passwd
00000000  72 6f 6f 74 3a 78 3a 30  3a 30 3a 72 6f 6f 74 3a  |root:x:0:0:root:|
00000010  2f 72 6f 6f 74 3a 2f 62  69 6e 2f 62 61 73 68 0a  |/root:/bin/bash.|
00000020  64 61 65 6d 6f 6e 3a 78  3a 31 3a 31 3a 64 61 65  |daemon:x:1:1:dae|
00000030  6d 6f 6e 3a 2f 75 73 72  2f 73 62 69 6e 3a 2f 62  |mon:/usr/sbin:/b|
00000040  69 6e 2f 73 68 0a 62 69  6e 3a 78 3a 32 3a 32 3a  |in/sh.bin:x:2:2:|
00000050  62 69 6e 3a 2f 62 69 6e  3a 2f 62 69 6e 2f 73 68  |bin:/bin:/bin/sh|
...

Printing hexadecimal characters in C

You are seeing the ffffff because char is signed on your system. In C, vararg functions such as printf will promote all integers smaller than int to int. Since char is an integer (8-bit signed integer in your case), your chars are being promoted to int via sign-extension.

Since c0 and 80 have a leading 1-bit (and are negative as an 8-bit integer), they are being sign-extended while the others in your sample don't.

char    int
c0 -> ffffffc0
80 -> ffffff80
61 -> 00000061

Here's a solution:

char ch = 0xC0;
printf("%x", ch & 0xff);

This will mask out the upper bits and keep only the lower 8 bits that you want.

Reading file in hex gives wrong output (skips some hex values)

Operator>> reads formatted data (char in your case) from the input stream, so a char with value 12 (0c in hex) is considered as ASCII form feed and ignored ( as a value of 32 or 0x20 would be considered a space ).
Char are also signed values and an hex value of a2 (which is decimal 162) would be stored as a negative value. Promoting that value to an int would keep the sign and due to complementation, when printed as unsigned you'll get the ffff's.

keep the

unsigned char input;

then to read the values use

inf.get(static_cast<char>(input))

and to print

cout << hex << setw(2) << setfill('0') << static_cast<unsigned int>(input) << " ";

Conversion hex string into ascii in bash command line

This worked for me.

$ echo 54657374696e672031203220330 | xxd -r -p
Testing 1 2 3$

-r tells it to convert hex to ascii as opposed to its normal mode of doing the opposite

-p tells it to use a plain format.

Ascii/Hex convert in bash

The reason is because hexdump by default prints out 16-bit integers, not bytes. If your system has them, hd (or hexdump -C) or xxd will provide less surprising outputs - if not, od -t x1 is a POSIX-standard way to get byte-by-byte hex output. You can use od -t x1c to show both the byte hex values and the corresponding letters.

If you have xxd (which ships with vim), you can use xxd -r to convert back from hex (from the same format xxd produces). If you just have plain hex (just the '4161', which is produced by xxd -p) you can use xxd -r -p to convert back.

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