Peculiarity of -B and -A command line options of bgrep

[sdbbs]

In normal grep, I'm used to e.g. -B2 to mean "two lines before current match", and -A2 to mean "two lines after current match", for instance:

$  echo -e '1\n2\n3\n4\n5\n6\n7\n8\n' | grep -B2 -A2 '4\|5' --color=always | cat --show-nonprinting
2
3
^[[01;31m^[[K4^[[m^[[K
^[[01;31m^[[K5^[[m^[[K
6
7

By analogy, my first thought is to apply the same interpretation for -B and -A command line options of bgrep as well, except expressed in bytes; however that interpretation does not seem to apply to bgrep - with -A2 and -B2 in the command below, I hoped to obtain two bytes before the match, and two bytes after the match, so 6 bytes in al:

$  echo -ne '\x01\x02\x03\x04\x05\x06\x07\x08' > test.bin && bgrep -B2 -A2 0405 test.bin
test.bin: 00000003
\x02\x03\x04\x05

.... however, I get only 4 matches. It seems, the problem is the -A switch, and in it, we have to add the expected length of the match, and the desired amount of bytes after, to obtain the desired behavior - meaning we need to use -B2 -A4 to obtain "two bytes before the match, and two bytes after the match": in the printout:

$  echo -ne '\x01\x02\x03\x04\x05\x06\x07\x08' > test.bin && bgrep -B2 -A4 0405 test.bin
test.bin: 00000003
\x02\x03\x04\x05\x06\x07
```

It would be nice to have this fixed - or at least to have a note in the help text.

[tmbinc]

Documented/fixed (for -C) in #31 .

I think -A is actually useful to not always include the full match, so I kept the behavior. -C will dump on both sides, so it makes sense to include the match itself.