c (short for "compare") allows you to compare arrays of bytes from different sources. The command accepts input in a number of formats, and then compares it against values found at current seek position.
[0x00404888]> c?
|Usage: c[?dfx] [argument]
| c [string] Compares a plain with escaped chars string
| cc [at] [(at)] Compares in two hexdump columns of block size
| c4 [value] Compare a doubleword from a math expression
| c8 [value] Compare a quadword from a math expression
| cx [hexpair] Compare hexpair string
| cX [addr] Like 'cc' but using hexdiff output
| cf [file] Compare contents of file at current seek
| cg[o] [file] Graphdiff current file and [file]
| cu [addr] @at Compare memory hexdumps of $$ and dst in unified diff
| cw[us?] [...] Compare memory watchers
| cat [file] Show contents of file (see pwd, ls)
| cl|cls|clear Clear screen, (clear0 to goto 0, 0 only)
To compare memory contents at current seek position against given string of values, use cx:
[0x08048000]> p8 4
7f 45 4c 46
[0x08048000]> cx 7f 45 90 46
Compare 3/4 equal bytes
0x00000002 (byte=03) 90 ' ' -> 4c 'L'
[0x08048000]>
Another subcommand of c command is cc which stands for "compare code".
To compare a byte sequence with a sequence in memory:
[0x4A13B8C0]> cc 0x39e8e089 @ 0x4A13B8C0
To compare contents of two functions specified by their names:
[0x08049A80]> cc sym.main2 @ sym.main
c8 compares a quadword from the current seek (in the example below, 0x00000000) against a math expression:
[0x00000000]> c8 4
Compare 1/8 equal bytes (0%)
0x00000000 (byte=01) 7f ' ' -> 04 ' '
0x00000001 (byte=02) 45 'E' -> 00 ' '
0x00000002 (byte=03) 4c 'L' -> 00 ' '
The number parameter can of course also be a math expressions which uses flag names etc:
[0x00000000]> cx 7f469046
Compare 2/4 equal bytes
0x00000001 (byte=02) 45 'E' -> 46 'F'
0x00000002 (byte=03) 4c 'L' -> 90 ' '
You can use compare command to find differences between a current block and a file previously dumped to a disk:
r2 /bin/true
[0x08049A80]> s 0
[0x08048000]> cf /bin/true
Compare 512/512 equal bytes