How do I compare binary files in Linux?

As ~quack pointed out:

 % xxd b1 > b1.hex
 % xxd b2 > b2.hex

And then

 % diff b1.hex b2.hex

or

 % vimdiff b1.hex b2.hex

This will print the offset and bytes in hex:

cmp -l file1.bin file2.bin | gawk '{printf "%08X %02X %02X\n", $1, strtonum(0$2), strtonum(0$3)}'

Or do $1-1 to have the first printed offset start at 0.

cmp -l file1.bin file2.bin | gawk '{printf "%08X %02X %02X\n", $1-1, strtonum(0$2), strtonum(0$3)}'

Unfortunately, strtonum() is specific to GAWK, so for other versions of awk—e.g., mawk—you will need to use an octal-to-decimal conversion function. For example,

cmp -l file1.bin file2.bin | mawk 'function oct2dec(oct,     dec) {for (i = 1; i <= length(oct); i++) {dec *= 8; dec += substr(oct, i, 1)}; return dec} {printf "%08X %02X %02X\n", $1, oct2dec($2), oct2dec($3)}'

Broken out for readability:

cmp -l file1.bin file2.bin |
    mawk 'function oct2dec(oct,    dec) {
              for (i = 1; i <= length(oct); i++) {
                  dec *= 8;
                  dec += substr(oct, i, 1)
              };
              return dec
          }
          {
              printf "%08X %02X %02X\n", $1, oct2dec($2), oct2dec($3)
          }'

There's a tool called DHEX which may do the job, and there's another tool called VBinDiff.

For a strictly command-line approach, try jojodiff.

diff + od method that works for byte addition / deletion

diff <(od -An -tx1 -w1 -v file1) \
     <(od -An -tx1 -w1 -v file2)

which you may want to alias in Bash as:

bdiff() {
  diff <(od -An -tx1 -w1 -v "$1") \
       <(od -An -tx1 -w1 -v "$2")
}

Generate a test case with a single removal of byte 64:

for i in `seq 128`; do printf "%02x" "$i"; done | xxd -r -p > file1
for i in `seq 128`; do if [ "$i" -ne 64 ]; then printf "%02x" $i; fi; done | xxd -r -p > file2

Output:

64d63
<  40

If you also want to see the ASCII version of the character:

bdiff() (
  f() (
    od -An -tx1c -w1 -v "$1" | paste -d '' - -
  )
  diff <(f "$1") <(f "$2")
)

bdiff file1 file2

Output:

64d63
<   40   @

Tested on Ubuntu 16.04.

I prefer od over xxd because:

• it is POSIX, xxd is not (comes with Vim)
• has the -An to remove the address column without awk.

Command explanation:

• -An removes the address column. This is important otherwise all lines would differ after a byte addition / removal.
• -w1 puts one byte per line, so that diff can consume it. It is crucial to have one byte per line, or else every line after a deletion would become out of phase and differ. Unfortunately, this is not POSIX, but present in GNU.
• -tx1 is the representation you want, change to any possible value, as long as you keep 1 byte per line.
• -v prevents asterisk repetition abbreviation * which might interfere with the diff
• paste -d '' - - joins every two lines. We need it because the hex and ASCII go into separate adjacent lines. Taken from: https://stackoverflow.com/questions/8987257/concatenating-every-other-line-with-the-next
• we use parenthesis () to define bdiff instead of {} to limit the scope of the inner function f, see also: https://stackoverflow.com/questions/8426077/how-to-define-a-function-inside-another-function-in-bash

See also:

• https://unix.stackexchange.com/questions/59849/diff-binary-files-of-different-sizes
• https://stackoverflow.com/questions/8385618/using-cmp-to-compare-two-binaries