rasm2 is an inline assembler/disassembler. Initially, rasm tool was designed to be used for binary patching. It is main function is get bytes corresponding to given machine instruction opcode.
$ rasm2 -h
Usage: rasm2 [-CdDehLBvw] [-a arch] [-b bits] [-o addr] [-s syntax]
[-f file] [-F fil:ter] [-i skip] [-l len] 'code'|hex|-
-a [arch] Set architecture to assemble/disassemble (see -L)
-b [bits] Set cpu register size (8, 16, 32, 64) (RASM2_BITS)
-c [cpu] Select specific CPU (depends on arch)
-C Output in C format
-d, -D Disassemble from hexpair bytes (-D show hexpairs)
-e Use big endian instead of little endian
-f [file] Read data from file
-F [in:out] Specify input and/or output filters (att2intel, x86.pseudo, ...)
-h Show this help
-i [len] ignore/skip N bytes of the input buffer
-k [kernel] Select operating system (linux, windows, darwin, ..)
-l [len] Input/Output length
-L List supported asm plugins
-o [offset] Set start address for code (default 0)
-O [file] Output file name (rasm2 -Bf a.asm -O a)
-s [syntax] Select syntax (intel, att)
-B Binary input/output (-l is mandatory for binary input)
-v Show version information
-w What's this instruction for? describe opcode
If '-l' value is greater than output length, output is padded with nops
If the last argument is '-' reads from stdin
Plugins for supported target architectures can be listed with the -L option. Knowing a plugin name, you can use it by specifying its name to the -a option
$ rasm2 -L
_d 16 8051 PD 8051 Intel CPU
_d 16 32 arc GPL3 Argonaut RISC Core
ad 16 32 64 arm GPL3 Acorn RISC Machine CPU
_d 16 32 64 arm.cs BSD Capstone ARM disassembler
_d 16 32 arm.winedbg LGPL2 WineDBG's ARM disassembler
_d 16 32 avr GPL AVR Atmel
ad 32 bf LGPL3 Brainfuck
_d 16 cr16 LGPL3 cr16 disassembly plugin
_d 16 csr PD Cambridge Silicon Radio (CSR)
ad 32 64 dalvik LGPL3 AndroidVM Dalvik
ad 16 dcpu16 PD Mojang's DCPU-16
_d 32 64 ebc LGPL3 EFI Bytecode
_d 8 gb LGPL3 GameBoy(TM) (z80-like)
_d 16 h8300 LGPL3 H8/300 disassembly plugin
_d 8 i8080 BSD Intel 8080 CPU
ad 32 java Apache Java bytecode
_d 32 m68k BSD Motorola 68000
_d 32 malbolge LGPL3 Malbolge Ternary VM
ad 32 64 mips GPL3 MIPS CPU
_d 16 32 64 mips.cs BSD Capstone MIPS disassembler
_d 16 32 64 msil PD .NET Microsoft Intermediate Language
_d 32 nios2 GPL3 NIOS II Embedded Processor
_d 32 64 ppc GPL3 PowerPC
_d 32 64 ppc.cs BSD Capstone PowerPC disassembler
ad rar LGPL3 RAR VM
_d 32 sh GPL3 SuperH-4 CPU
_d 32 64 sparc GPL3 Scalable Processor Architecture
_d 32 tms320 LGPLv3 TMS320 DSP family
_d 32 ws LGPL3 Whitespace esotheric VM
_d 16 32 64 x86 BSD udis86 x86-16,32,64
_d 16 32 64 x86.cs BSD Capstone X86 disassembler
a_ 32 64 x86.nz LGPL3 x86 handmade assembler
ad 32 x86.olly GPL2 OllyDBG X86 disassembler
ad 8 z80 NC-GPL2 Zilog Z80
Note that "ad" in the first column means both assembler and disasembler are offered by a corresponding plugin. "d" indicates disassembler, "a" means only assembler is available.