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I have a very long text file (from here) which should contain 6 hexadecimal characters then a 'break' (which appears as one character and doesn't seem to show up properly in the code markdown below) followed by a few words:

00107B Cisco Systems, Inc
00906D Cisco Systems, Inc
0090BF Cisco Systems, Inc
5080 Cisco Systems, Inc
0E+00 ASUSTek COMPUTER INC.
000C6E ASUSTek COMPUTER INC.
001BFC ASUSTek COMPUTER INC.
001E8C ASUSTek COMPUTER INC.
0015F2 ASUSTek COMPUTER INC.
2354 ASUSTek COMPUTER INC.
001FC6 ASUSTek COMPUTER INC.
60182E ShenZhen Protruly Electronic Ltd co.
F4CFE2 Cisco Systems, Inc
501CBF Cisco Systems, Inc

I've done some looking around and can't see something which would work in this situation. My question is, how can I use grep/sed/awk/perl to delete all lines of this text file which do not start with exactly 6 hexadecimal characters and then a 'break'?

P.S. For bonus points, what's the best way of sorting the file alphabetically and numerically according to the hex characters (i.e. 000000 -> FFFFFF)? Should I just use sort?

$ awk '$1 ~ /^[[:xdigit:]]6$/' file
00107B Cisco Systems, Inc
00906D Cisco Systems, Inc
0090BF Cisco Systems, Inc
000C6E ASUSTek COMPUTER INC.
001BFC ASUSTek COMPUTER INC.
001E8C ASUSTek COMPUTER INC.
0015F2 ASUSTek COMPUTER INC.
001FC6 ASUSTek COMPUTER INC.
60182E ShenZhen Protruly Electronic Ltd co.
F4CFE2 Cisco Systems, Inc
501CBF Cisco Systems, Inc

This uses awk to extract the lines that contains exactly six hexadecimal digits in the first field. The [[:xdigit:]] pattern matches a hexadecimal digit, and 6 requires six of them. Together with the anchoring to the start and end of the field with ^ and $ respectively, this will only match on the wanted lines.

Redirect to some file to save it under a new name.

Note that this seems to work with GNU awk (commonly found on Linux), but not with awk on e.g. OpenBSD, or mawk.

A similar approach with sed:

$ sed -n '/^[[:xdigit:]]6>/p' file
00107B Cisco Systems, Inc
00906D Cisco Systems, Inc
0090BF Cisco Systems, Inc
000C6E ASUSTek COMPUTER INC.
001BFC ASUSTek COMPUTER INC.
001E8C ASUSTek COMPUTER INC.
0015F2 ASUSTek COMPUTER INC.
001FC6 ASUSTek COMPUTER INC.
60182E ShenZhen Protruly Electronic Ltd co.
F4CFE2 Cisco Systems, Inc
501CBF Cisco Systems, Inc

In this expression, > is used to match the end of the hexadecimal number. This ensures that longer numbers are not matched. The > pattern matches a word boundary, i.e. the zero-width space between a word character and a non-word character.

For sorting the resulting data, just pipe the result trough sort, or sort -f if your hexadecimal numbers uses both upper and lower case letters

And for completeness, you can do this with grep too:

$ grep -E '^[[:xdigit:]]6b' oui.txt 
00107B Cisco Systems, Inc
00906D Cisco Systems, Inc
0090BF Cisco Systems, Inc
000C6E ASUSTek COMPUTER INC.
001BFC ASUSTek COMPUTER INC.
001E8C ASUSTek COMPUTER INC.
0015F2 ASUSTek COMPUTER INC.
001FC6 ASUSTek COMPUTER INC.
60182E ShenZhen Protruly Electronic Ltd co.
F4CFE2 Cisco Systems, Inc
501CBF Cisco Systems, Inc
$ 

This extended grep expression searches for exactly 6 hex digits at the beginning of each line, followed immediately by a non-whitespace-to-whitespace boundary (b).