DEX files are embeded in Android ART .oat/.odex files. oat2dexes
looks for
DEX magic "dex\n035\0".
$ file file.odex
file.odex: ELF 32-bit LSB shared object, ARM, version 1 (GNU/Linux), dynamically linked, stripped
$ gcc -o oat2dexes -Wall oat2dexes.c
$ ./oat2dexes file.odex
Writing 12345 bytes to dex01.dex
$ java -jar baksmali.jar -o outdir dex01.dex