Additional Whitespace and line-breaks are allowed anywhere. Without -s option, xxd starts at the current file position. Default is lower case. If the ouput file is seekable, then the linenumbers at the start of each hexdump line may be out of order, lines may be missing, or overlapping. If the output file is not seekable, only gaps are allowed, which will be filled by null-bytes.
Garbage is silently skipped.
Here an thing that looks like a pair of hex-digits is interpreted. 7363746e7567656e2e7070702e67752e6564752e Hexdump the first 120 bytes of this man page with 12 octets per line. 2e67 752e 6564 752e .ppp.gu.edu. Hexdump this file with autoskip. A Create a 1 byte file containing a single 'A' character.