Linux Pocket Guide, 2nd Edition

Name

od — stdin  stdout  - file  -- opt  --help  --version

Synopsis

od [options] [files]

When you want to view a binary file, consider od (Octal Dump) for the job. It copies one or more files to standard output, displaying their data in ASCII, octal, decimal, hexadecimal, or floating point, in various sizes (byte, short, long). For example, this command:

$ od -w8 /usr/bin/who
0000000 042577 043114 000401 000001
0000010 000000 000000 000000 000000
0000020 000002 000003 000001 000000
...

displays the bytes in binary file /usr/bin/who in octal, eight bytes per line. The column on the left contains the file offset of each row, again in octal.

If your binary file also contains text, consider the -tc option, which displays character data. For example, binary executables like who contain the string “ELF” at the beginning:

$ od -tc -w8 /usr/bin/who | head -3
0000000 177   E   L   F 001 001 001  \0
0000010  \0  \0  \0  \0  \0  \0  \0  \0
0000020 002  \0 003  \0 001  \0  \0  \0

Useful options

-N B	Display only the first B bytes of each file, specified in decimal, hexadecimal (by prepending 0x or 0X), 512-byte blocks (by appending b), kilobytes (by appending k), or megabytes (by appending m). (Default displays the entire file.)
-j B	Begin the output at byte B +1 of each file; acceptable formats are the same as for the -N option. (Default=0)
-w [ B ]	Display B bytes per line; acceptable formats are the same as in the -N option. Using -w by itself is equivalent to -w32. (Default=16)
-s [ B ]	Group each row of bytes ...