Shell Programming and Scripting

can anyone please explain this code?

Code:

sed ':a;N;$!ba;s/]\n//g' file

it replaces lines ending with "]" and concatenates with the next line so that

Code:

line1]
line2

becomes

Code:

line1line2

i don't understand this part:

Code:

:a;N;$!ba;

I have noted that I can replace "a" with any letter:

Code:

:c;N;$!bc;

works fine!

: introduces a label. b branches to a label. $! is an address that matches all but the last line. :a;N;$!ba; is a loop which joins lines (using N) until it gets to the last line.

Regards,
Alister

---------- Post updated at 07:08 PM ---------- Previous update was at 07:02 PM ----------

By the way, should that sed script not work on some implementations, it's because using a semicolon to terminate a label is forbidden by POSIX. GNU sed (perhaps others) allows it, but not all do and it's not required.