I am currently reading a very old reference from O'Reilly: Sed and Awk 2nd Edition reprinted in 2000. So far, it's a solid read and still very relevant. I'd highly recommend this to anyone.
The only problem I have with this book is that I had to resort to bourne shell to get my examples to work since bash wasn't ubiquitous when the book was written.
So, when I was trying to follow the book example, I get the error in bash on my latest Ubuntu Server distro.
I tried to use a regular expression that looked for any line containing the string, "book" in the bookworks file. It is not my ultimate goal to correctly extract all lines with the string "book" yet as I was following the book examples, which will show me the correct form.
I tried the following command in bash:
Code:
grep " [\"[{(]*book[]})\"?!.,;:'s]* " bookwords
I get the following error in bash:
Code:
-bash: !.,: event not found
But when I tried the command after switching over to bourne shell, I get no error, and it gave me the output I expected like the one in the book examples. Can someone please tell me why is this happening? I'd like to know what metacharacters are causing this and how I can escape it in Bash? I wish there is a third edition of this book that covers REGEX in bash.
That is because of bash's history expansion. It tries to expand the exclamation mark. Try switching it off first:
Code:
set +H
Then it should work.
You could also escape the exclamation mark(s):
Code:
grep " [\"[{(]*book[]})\"?\!.,;:'s]* " bookwords
Or use single quotes but in your example they use double quotes in order to use a single quote in the expression. You could make a combination of a string that is part in single quotes, followed by a part in double quotes:
Code:
grep '["[{(]*book[]})"?!.,;:'"'s]* " bookwords
Last edited by Scrutinizer; 03-20-2013 at 12:55 PM..
This User Gave Thanks to Scrutinizer For This Post:
That it's willing to expand history !'s inside quotes is one of the very few things that really enrages me about bash... A character that expands when quoted and doesn't when not, but only at certain times and not others, seems very hacky.
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03-20-2013
