[SOLVED] sed with RegEx

danielbmartin · 08-06-2012, 05:57 PM

Have: a file such as this...

Code:

H421J224 Walter Philip George Henry
John Louis H76K3 David Roland H9J8 
James H654J3439 Thomas H0J9 Edward
Kenneth Harold HJ Joseph Ronald Jason

Want: a sed which uses a Regular Expression to remove all character strings which fit this description:
H
one or more digits
J
one or more digits
one blank (unless the match is at the end of a line)

So, H421J224 would be eliminated but H76K3 would not.

I've been stumbling around with this...

Code:

sed -r 's/H[:digit:]+J[:digit:]+[:space:]+//g'

... to no avail.

Please advise.

Daniel B. Martin

pixellany · 08-06-2012, 06:37 PM

first, you need to put character classes in double brackets---eg [[:digit:]]

Assuming that's fixed, then the last one translates to "one or more spaces"---that's not what you say you wanted.

When you say
"one blank (unless the match is at the end of a line)"
do you mean:
"one blank if NOT at the end of line"?

towheedm · 08-06-2012, 06:44 PM

First, using the -r option to SED, tells it to use Extended Regex (ERE) not Regex (RE). Using the + modifier as part of an ERE does not require that you escape it.

Code:

sed -r 's/H[0-9]+J[0-9]+ ?//g'    # or if you must use POSIX char sets
sed -r 's/H[[:digit:]]+J[[:digit:]]+[[:space:]]?//g

Using the + modifier as you did will try to match one or more whitespaces at the end of the line. Since there is no whitespace at the end of the line, it will always fails. Use the ? modifier to match zero or more spaces, which will find a match even at the end of the line.

Hope this helps.

danielbmartin · 08-06-2012, 09:36 PM

Quote:

Originally Posted by pixellany

When you say
"one blank (unless the match is at the end of a line)"
do you mean:
"one blank if NOT at the end of line"?

Yes. Your wording is better.

Daniel B. Martin

danielbmartin · 08-06-2012, 09:40 PM

Quote:

Originally Posted by towheedm

Code:

sed -r 's/H[0-9]+J[0-9]+ ?//g'

I used this and like it because it uses fewer keystrokes and is more readable (IMHO).

Thank you.

Daniel B. Martin