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The block size determines how many bytes radare2 commands will process when not given an explicit size argument. You can temporarily change the block size by specifying a numeric argument to the print commands. For example `px 20`.
[0x00000000]> b? Usage: b[f] [arg] # Get/Set block size | b 33 set block size to 33 | b eip+4 numeric argument can be an expression | b display current block size | b+3 increase blocksize by 3 | b-16 decrease blocksize by 16 | b* display current block size in r2 command | bf foo set block size to flag size | bj display block size information in JSON | bm 1M set max block size
The `b` command is used to change the block size:
[0x00000000]> b 0x100 # block size = 0x100 [0x00000000]> b+16 # ... = 0x110 [0x00000000]> b-32 # ... = 0xf0
The `bf` command is used to change the block size to value specified by a flag. For example, in symbols, the block size of the flag represents the size of the function. To make that work, you have to either run function analysis `af` (which is included in `aa`) or manually seek and define some functions e.g. via `Vd`.
[0x00000000]> bf sym.main # block size = sizeof(sym.main) [0x00000000]> pD @ sym.main # disassemble sym.main
You can combine two operations in a single `pdf` command. Except that `pdf` neither uses nor affects global block size.
[0x00000000]> pdf @ sym.main # disassemble sym.main
Another way around is to use special variables `$FB` and `$FS` which denote Function's Beginning and Size at the current seek. Read more about Usable variables[1].
[0x00000000]> s sym.main + 0x04 [0x00001ec9]> pD @ $FB !$FS # disassemble current function / 211: int main (int argc, char **argv, char **envp); | 0x00001ec5 55 push rbp | 0x00001ec6 4889e5 mov rbp, rsp | 0x00001ec9 4881ecc0000000 sub rsp, 0xc0 ... \ 0x00001f97 c3 ret
Note: don't put space after `!` size designator. See also Command Format[1].